GNU General Public License

The GNU General Public License (GNU GPL or GPL) is a widely used free software license, which guarantees end users the freedoms to run, study, share (copy), and modify the software - wikipedia

Software that allows these rights is called Free Software and, if the software is copylefted, requires those rights to be retained.

The GPL demands both. The license was originally written by Richard Stallman of the Free Software Foundation (FSF) for the GNU Project.

In other words, the GPL grants the recipients of a computer program the rights of the Free Software Definition and uses copyleft to ensure the freedoms are preserved whenever the work is distributed, even when the work is changed or added to.

The GPL is a copyleft license, which means that derived works can only be distributed under the same license terms. This is in distinction to permissive free software licenses, of which the BSD licenses and the MIT License are the standard examples. GPL was the first copyleft license for general use.

Prominent free software programs licensed under the GPL include the Linux kernel and the GNU Compiler Collection (GCC). Some other free software programs (MySQL is a prominent example) are dual-licensed under multiple licenses, often with one of the licenses being the GPL.

Historically, the GPL license family has been one of the most popular software licenses in the FOSS domain. David A. Wheeler argues that the copyleft provided by the GPL was crucial to the success of Linux-based systems, giving the programmers who contributed to the kernel the assurance that their work would benefit the whole world and remain free, rather than being exploited by software companies that would not have to give anything back to the community.

On 29 June 2007, the third version of the license (GNU GPLv3) was released to address some perceived problems with the second version (GNU GPLv2) that were discovered during its long-time usage. To keep the license up-to-date, the GPL license includes an optional "any later version" clause, allowing users to choose between the original terms or the terms in new versions as updated by the FSF. Developers can omit it when licensing their software; for instance the Linux kernel is licensed under GPLv2 without the "any later version" clause.

The GPL was written by Richard Stallman in 1989, for use with programs released as part of the GNU project. The original GPL was based on a unification of similar licenses used for early versions of GNU Emacs (1985),GNU Emacs Copying Permission Notice (1985) the GNU Debugger and the GNU C Compiler (GNU Compiler Collection).[ ] These licenses contained similar provisions to the modern GPL, but were specific to each program, rendering them incompatible, despite being the same license.[ ] Stallman's goal was to produce one license that could be used for any project, thus making it possible for many projects to share code.

The second version of the license, version 2, was released in 1991. Over the following 15 years, members of the free software community became concerned over problems in the GPLv2 license that could let someone exploit GPL-licensed software in ways contrary to the license's intent.[ ] These problems included tivoization (the inclusion of GPL-licensed software in hardware that refuses to run modified versions of its software), compatibility issues similar to those of the Affero General Public License—and patent deals between Microsoft and distributors of free and open source software, which some viewed as an attempt to use patents as a weapon against the free software community.

Version 3 was developed to attempt to address these concerns and was officially released on 29 June 2007.

The terms and conditions of the GPL must be made available to anybody receiving a copy of the work that has a GPL applied to it ("the licensee"). Any licensee who adheres to the terms and conditions is given permission to modify the work, as well as to copy and redistribute the work or any derivative version. The licensee is allowed to charge a fee for this service, or do this free of charge. This latter point distinguishes the GPL from software licenses that prohibit commercial redistribution. The FSF argues that free software should not place restrictions on commercial use,Selling Free Software and the GPL explicitly states that GPL works may be sold at any price.

The GPL additionally states that a distributor may not impose "further restrictions on the rights granted by the GPL". This forbids activities such as distributing of the software under a non-disclosure agreement or contract. Distributors under the GPL also grant a license for any of their patents practiced by the software, to practice those patents in GPL software.Category:All articles with unsourced statementsCategory:Articles with unsourced statements from July 2015<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">&#91;<i><span title="This claim needs references to reliable sources.<nowiki/> (July 2015)">citation needed</span> (Wikipedia:Citation needed)</i>&#93;</sup>

The fourth section for version 2 of the license and the seventh section of version 3 require that programs distributed as pre-compiled binaries are accompanied by a copy of the source code, a written offer to distribute the source code via the same mechanism as the pre-compiled binary, or the written offer to obtain the source code that the user got when they received the pre-compiled binary under the GPL. The second section of version 2 and the fifth section of version 3 also require giving "all recipients a copy of this License along with the Program". Version 3 of the license allows making the source code available in additional ways in fulfillment of the seventh section. These include downloading source code from an adjacent network server or by peer-to-peer transmission, provided that is how the compiled code was available and there are "clear directions" on where to find the source code.

The FSF does not hold the copyright for a work released under the GPL, unless an author explicitly assigns copyrights (Copyright assignment) to the FSF (which seldom happens except for programs that are part of the GNU project). Only the individual copyright holders have the authority to sue when a license violation takes place.

Software under the GPL may be run for all purposes, including commercial purposes and even as a tool for creating proprietary software, for example when using GPL-licensed compilers.<ref>GPL FAQ: Use GPL Tools to develop non-free programs </ref> Users or companies who distribute GPL-licensed works (e.g. software), may charge a fee for copies or give them free of charge. This distinguishes the GPL from shareware software licenses that allow copying for personal use but prohibit commercial distribution, or proprietary licenses where copying is prohibited by copyright law. The FSF argues that freedom-respecting free software should also not restrict commercial use and distribution (including redistribution):<ref name="Selling Free Software"/> the GPL explicitly states that GPL works may be sold at any price.

In purely private (or internal) use —with no sales and no distribution— the software code may be modified and parts reused without requiring the source code to be released. For sales or distribution, the entire source code need to be made available to end users, including any code changes and additions— in that case, copyleft is applied to ensure that end users retain the freedoms defined above.<ref>GPL FAQ: GPL require source posted to public , Unreleased modifications , Internal Distribution </ref>

However, software running as an application program under a GPL-licensed operating system such as Linux is not required to be licensed under GPL or to be distributed with source-code availability—the licensing depends only on the used libraries and software components and not on the underlying platform.<ref name=portlinux>GPL FAQ: Port program to GNU/Linux </ref> For example, if a program consists only of own original custom software, or is combined with source code from other software components,<ref>example: if ''only'' GNU ''Lesser'' General Public License (GNU Lesser General Public License)- (LGPL-) libraries, LGPL-software-components and components with permissive free software licenses are used (thus not GPL itself), then ''only'' the source code of LGPL parts has to be made available— for the developer's own self-developed software components this is not required (even when the underlying operating system used is licensed under GPL, as is the case with Linux).</ref> then the own custom software components need not be licensed under GPL and need not make their code available; even if the underlying operating system used is licensed under the GPL, applications running on it are not considered derivative works.<ref name=portlinux /> Only if GPLed parts are used in a program (and the program is distributed), then all other source code of the program needs to be made available under the same license terms. The GNU ''Lesser'' General Public license (GNU Lesser General Public License) (LGPL) was created to have a weaker copyleft than the GPL, in that it does not require own custom-developed source code (distinct from the LGPLed parts) to be made available under the same license terms.

The distribution rights granted by the GPL for modified versions of the work are not unconditional. When someone distributes a GPL'd work plus his/her own modifications, the requirements for distributing the whole work cannot be any greater than the requirements that are in the GPL.

This requirement is known as copyleft. It earns its legal power from the use of copyright on software programs. Because a GPL work is copyrighted, a licensee has no right to redistribute it, not even in modified form (barring fair use), except under the terms of the license. One is only required to adhere to the terms of the GPL if one wishes to exercise rights normally restricted by copyright law, such as redistribution. Conversely, if one distributes copies of the work without abiding by the terms of the GPL (for instance, by keeping the source code secret), he or she can be sued (lawsuit) by the original author under copyright law.

Copyleft thus uses copyright law to accomplish the opposite of its usual purpose: instead of imposing restrictions, it grants rights to other people, in a way that ensures the rights cannot subsequently be taken away. It also ensures that unlimited redistribution rights are not granted, should any legal flaw be found in the copyleft statement.Category:All articles with unsourced statementsCategory:Articles with unsourced statements from September 2011<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">&#91;<i><span title="This claim needs references to reliable sources.<nowiki/> (September 2011)">citation needed</span> (Wikipedia:Citation needed)</i>&#93;</sup>

Many distributors of GPL'ed programs bundle the source code with the executables. An alternative method of satisfying the copyleft is to provide a written offer to provide the source code on a physical medium (such as a CD) upon request. In practice, many GPL'ed programs are distributed over the Internet, and the source code is made available over FTP (File Transfer Protocol) or HTTP (Hypertext Transfer Protocol). For Internet distribution, this complies with the license.

Copyleft applies only when a person seeks to redistribute the program. Developers may make private modified versions with no obligation to divulge the modifications, as long as they don't distribute the modified software to anyone else. Note that copyleft applies only to the software, and not to its output (unless that output is itself a derivative work of the program<ref>A counter example is the GPL'ed GNU Bison: the parsers it outputs ''do'' contain parts of itself and are therefore derivatives, which would fall under the GPL if not for a special exception granted by GNU Bison: </ref>). For example, a public web portal running a modified derivative of a GPL'ed content management system is not required to distribute its changes to the underlying software, because its output is not a derivative.

There has been debate on whether it is a violation of the GPL to release the source code in obfuscated (obfuscation (software)) form, such as in cases in which the author is less willing to make the source code available. The consensus was that while unethical, it was not considered a violation. The issue was clarified when the license was altered with v2 to require that the "preferred" version of the source code be made available.Reasoning behind the "preferred form" language in the GPL

The GPL was designed as a license, rather than a contract.Essay by Stallman explaining why a license is more suitable than a contract Eben Moglen explaining why the GPL is a license and why it matters In some Common Law jurisdictions, the legal distinction between a license and a contract is an important one: contracts are enforceable by contract law, whereas licenses are enforced under copyright law. However, this distinction is not useful in the many jurisdictions where there are no differences between contracts and licenses, such as Civil Law (Civil law (legal system)) systems.[ ]

Those who do not accept the GPL's terms and conditions do not have permission, under copyright law, to copy or distribute GPL licensed software or derivative works. However, if they do not redistribute the GPL'd program, they may still use the software within their organization however they like, and works (including programs) constructed by the use of the program are not required to be covered by this license.

Allison Randal argued that the GPLv3 as a license is unnecessarily confusing for lay readers, and could be simplified while retaining the same conditions and legal force.GPLv3, Clarity and Simplicity

The text of the GPL is itself copyrighted, and the copyright is held by the Free Software Foundation.

The FSF permits people to create new licenses based on the GPL, as long as the derived licenses do not use the GPL preamble without permission. This is discouraged, however, since such a license might be incompatible with the GPLGPL FAQ: Can I modify the GPL and make a modified license? and causes a perceived license proliferation.

Other licenses created by the GNU project include the GNU Lesser General Public License, the GNU Free Documentation License and Affero General Public License (GNU Affero General Public License)

The text of the GPL is not itself under the GPL. The license's copyright disallows modification of the license. Copying and distributing the license is allowed since the GPL requires recipients to get "a copy of this License along with the Program".The GNU General Public License Version 3 According to the GPL FAQ, anyone can make a new license using a modified version of the GPL as long as he or she uses a different name for the license, does not mention "GNU", and removes the preamble, though the preamble can be used in a modified license if permission to use it is obtained from the Free Software Foundation (FSF) (Free Software Foundation).

According to the FSF (Free Software Foundation), "The GPL does not require you to release your modified version, or any part of it. You are free to make modifications and use them privately, without ever releasing them."GPL FAQ: Does the GPL require that source code of modified versions be posted to the public? However, if one releases a GPL-licensed entity to the public, there is an issue regarding linking: namely, whether a proprietary program that uses a GPL library is in violation of the GPL.

This key dispute is whether or not non-GPL software can legally statically link (static linking) or dynamically link (dynamic linking) to GPL libraries. Different opinions exist on this issue. The GPL is clear in requiring that all derivative works of code under the GPL must themselves be under the GPL. Ambiguity arises with regards to using GPL libraries, and bundling GPL software into a larger package (perhaps mixed into a binary via static linking). This is ultimately a question not of the GPL ''per se'', but of how copyright law defines derivative works. The following points of view exist:

The Free Software Foundation (which holds the copyright of several notable GPL-licensed software products and of the license text itself) asserts that an executable which uses a dynamically linked library is indeed a derivative work. This does not however apply to separate programs communicating with one another.[ ]

The Free Software Foundation also created the LGPL, which is nearly identical to the GPL, but with additional permissions to allow linking for the purposes of "using the library".

Richard Stallman and the FSF specifically encourage library-writers to license under the GPL so that proprietary programs cannot use the libraries, in an effort to protect the free-software world by giving it more tools than the proprietary world.[ ]

Some people believe that while static linking produces derivative works, it is not clear whether an executable that dynamically links to a GPL code should be considered a derivative work (see Weak Copyleft (Weak copyleft)). Linux author Linus Torvalds agrees that dynamic linking can create derived works but disagrees over the circumstances.<ref>Linus Torvalds, GPL only modules , ''linux-kernel'' mailing list (17 December 2006).</ref>

A Novell lawyer has written that dynamic linking not being derivative "makes sense" but is not "clear-cut", and that evidence for good-intentioned dynamic linking can be seen by the existence of proprietary Linux kernel drivers.<ref>Matt Asay, The GPL: Understanding the License that Governs Linux , ''Novell Cool Solutions Feature'' (16 Jan 2004).</ref>

In ''Galoob v. Nintendo'' the United States Ninth Circuit Court of Appeals defined a derivative work as having "'form' or permanence" and noted that "the infringing work must incorporate a portion of the copyrighted work in some form", but there have been no clear court decisions to resolve this particular conflict.

According to an article in the Linux Journal, Lawrence Rosen (Lawrence Rosen (attorney)) (a one-time OSI (Open Source Initiative) general counsel) argues that the method of linking is mostly irrelevant to the question about whether a piece of software is a derivative work; more important is the question about whether the software was intended to interface with client software and/or libraries.<ref name=Rosen>Lawrence Rosen, Derivative Works , ''Linux Journal'' (1 January 2003).</ref>

He states, "The primary indication of whether a new program is a derivative work is whether the source code of the original program was used [in a copy-paste sense], modified, translated or otherwise changed in any way to create the new program. If not, then I would argue that it is not a derivative work,"<ref name=Rosen /> and lists numerous other points regarding intent, bundling, and linkage mechanism.

He further argues on his firm's website<ref>Lawrence Rosen, Derivative Works , ''rosenlaw.com'' (25 May 2004)</ref> that such "market-based" factors are more important than the linking technique.

There is also the specific issue of whether a plugin (Plug-in (computing)) or module (such as the NVidia or ATI (ATI (brand)) graphics card kernel modules) must also be GPL, if it could reasonably be considered its own work. This point of view suggests that reasonably separate plugins, or plugins for software designed to use plugins, could be licensed under an arbitrary license if the work is GPLv2. Of particular interest is the GPLv2 paragraph:

b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. [...] These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

It should be noted that the GPLv3 has a different clause:

c) You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable Section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it. [...] A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an "aggregate" if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

As a case study, some supposedly proprietary plugins and theme (theme (computing))s/skin (skin (computing))s for GPLv2 CMS (Content management system) software such as Drupal and WordPress have come under fire, with both sides of the argument taken.[ ][ ]

The FSF differentiates on how the plug-in is being invoked. If the Plug-in is invoked through dynamic linkage and it performs function calls to the GPL program then it is most likely a derivative work.[ ]

The mere act of communicating with other programs does not, by itself, require all software to be GPL; nor does distributing GPL software with non-GPL software. However, minor conditions must be followed that ensures the rights of GPL software is not restricted. The following is a quote from the gnu.org GPL FAQ, which describes to what extent software is allowed to communicate with and be-bundled-with GPL programs:

An "aggregate" consists of a number of separate programs, distributed together on the same CD-ROM or other media. The GPL permits you to create and distribute an aggregate, even when the licenses of the other software are non-free or GPL-incompatible. The only condition is that you cannot release the aggregate under a license that prohibits users from exercising rights that each program's individual license would grant them.

Where's the line between two separate programs, and one program with two parts? This is a legal question, which ultimately judges will decide. We believe that a proper criterion depends both on the mechanism of communication (exec, pipes, rpc, function calls within a shared address space, etc.) and the semantics of the communication (what kinds of information are interchanged).

If the modules are included in the same executable file, they are definitely combined in one program. If modules are designed to run linked together in a shared address space, that almost surely means combining them into one program.

By contrast, pipes, sockets and command-line arguments are communication mechanisms normally used between two separate programs. So when they are used for communication, the modules normally are separate programs. But if the semantics of the communication are intimate enough, exchanging complex internal data structures, that too could be a basis to consider the two parts as combined into a larger program.

The FSF thus draws the line between "library" and "other program" via 1) "complexity" and "intimacy" of information exchange, and 2) mechanism (rather than semantics), but resigns that the question is not clear-cut and that in complex situations, case law will decide.

The first known violation of the GPL was in 1989, when NeXT extended the GCC (GNU Compiler Collection) compiler to support Objective-C, but did not publicly release the changes.<ref>12 Years of GPL Compliance: A Historical Perspective , Slide 10</ref> After an inquiry they created a public patch (Patch (Unix)). There was no lawsuit filed for this violation.

In 2002, MySQL AB sued Progress NuSphere for copyright and trademark infringement in United States district court (U.S. District Court for the District of Massachusetts). NuSphere had allegedly violated MySQL's copyright by linking MySQL's GPL'ed code with NuSphere Gemini table without being in compliance with the license. After a preliminary hearing before Judge Patti Saris on 27 February 2002, the parties entered settlement talks and eventually settled.<ref>See ''Progress Software Corporation v. MySQL AB'', 195 F. Supp. 2d 328 (D. Mass. 2002), on defendant's motion for preliminary injunction.</ref> After the hearing, FSF commented that "Judge Saris made clear that she sees the GNU GPL to be an enforceable and binding license."[ ]

In August 2003, the SCO Group stated that they believed the GPL to have no legal validity, and that they intended to pursue lawsuits over sections of code supposedly copied from SCO Unix into the Linux kernel. This was a problematic stand for them, as they had distributed Linux and other GPL'ed code in their Caldera OpenLinux distribution, and there is little evidence that they had any legal right to do so except under the terms of the GPL. For more information, see SCO-Linux controversies and SCO v. IBM.

In April 2004, the netfilter/iptables project was granted a preliminary injunction against Sitecom Germany by Munich District Court after Sitecom refused to desist from distributing Netfilter's GPL'ed software in violation of the terms of the GPL. Harald Welte, of Netfilter, was represented by ifrOSS co-founder Till Jaeger. On July 2004, the German court confirmed this injunction as a final ruling against Sitecom.Groklaw - The German GPL Order - Translated The court's justification was that:

:Defendant has infringed on the copyright of plaintiff by offering the software 'netfilter/iptables' for download and by advertising its distribution, without adhering to the license conditions of the GPL. Said actions would only be permissible if defendant had a license grant... This is independent of the questions whether the licensing conditions of the GPL have been effectively agreed upon between plaintiff and defendant or not. If the GPL were not agreed upon by the parties, defendant would notwithstanding lack the necessary rights to copy, distribute, and make the software 'netfilter/iptables' publicly available.

This exactly mirrored the predictions given previously by the FSF's Eben Moglen. This ruling was important because it was the first time that a court had confirmed that violating terms of the GPL could be a copyright violation and established jurisprudence as to the enforceability of the GPL version 2 under German law.<ref>Bird & Bird, A Review of German Case Law on the GNU General Public License , 17 December 2007, retrieved 1 March 2012</ref>

In May 2005, Daniel Wallace filed suit (Wallace v. International Business Machines Corp. et al.) against the Free Software Foundation in the Southern District of Indiana (U.S. District Court for the Southern District of Indiana), contending that the GPL is an illegal attempt to fix prices (at zero). The suit was dismissed in March 2006, on the grounds that Wallace had failed to state a valid anti-trust claim; the court noted that "the GPL encourages, rather than discourages, free competition and the distribution of computer operating systems, the benefits of which directly pass to consumers".<ref name="groklawwallacevsfsfdismiss">Dismissal of Wallace v. FSF. From this article on Groklaw.</ref> Wallace was denied the possibility of further amending his complaint, and was ordered to pay the FSF's legal expenses.

On 8 September 2005, the Seoul Central District Court ruled that the GPL was not material to a case dealing with trade secrets derived from GPL-licensed work.판결문 - GNU 프로젝트 - 자유 소프트웨어 재단(FSF) Defendants argued that since it is impossible to maintain trade secrets while being compliant with GPL and distributing the work, they are not in breach of trade secrets. This argument was considered without ground.

On 6 September 2006, the gpl-violations.org project prevailed in court litigation against D-Link Germany GmbH regarding D-Link's copyright-infringing use of parts of the Linux Kernel in storage (Network-attached storage) devices they distributed.<ref>gpl-violations.org project prevails in court case on GPL violation by D-Link </ref> The judgment stated that the GPL is valid, legally binding, and stands in German court.<ref>D-Link Judgment (English translation) D-Link Judgement </ref>

In late 2007, the BusyBox developers and the Software Freedom Law Center embarked upon a program to gain GPL compliance from distributors of BusyBox in embedded systems, suing those who would not comply. These were claimed to be the first US uses of courts for enforcement of GPL obligations. ''See'' BusyBox GPL lawsuits (BusyBox#GPL lawsuits).

On 11 December 2008, the Free Software Foundation sued Cisco Systems, Inc. (Free Software Foundation v. Cisco Systems) for copyright violations by its Linksys division, of the FSF's GPL-licensed coreutils, readline, Parted, Wget, GNU Compiler Collection, binutils, and GNU Debugger software packages, which Linksys distributes in the Linux firmware[ ] of its WRT54G wireless routers, as well as numerous other devices including DSL and Cable modems, Network Attached Storage devices, Voice-Over-IP gateways, Virtual Private Network devices and a home theater/media player device.Free Software Foundation Files Suit Against Cisco For GPL Violations

After six years of repeated complaints to Cisco by the FSF, claims by Cisco that they would correct, or were correcting, their compliance problems (not providing complete copies of all source code and their modifications), of repeated new violations being discovered and reported with more products, and lack of action by Linksys (a process described on the FSF blog as a "five-years-running game of Whack-a-Mole"<ref name="FSF-Cisco"/>) the FSF took them to court.

Cisco settled the case six months later by agreeing "to appoint a Free Software Director for Linksys" to ensure compliance, "to notify previous recipients of Linksys products containing FSF programs of their rights under the GPL," to make source code of FSF programs freely available on its website, and to make a monetary contribution to the FSF.FSF Settles Suit Against Cisco

In 2011 it was noticed that GNU Emacs had violated its GPL license for the previous two years.Say what? GNU Emacs violates the GPL <ref>License revoked: Applying Section 4 of the GPL and the lessons of Best Buy to Google’s Android on brownrudnick.com by Edward J. Naughton (Aug 8, 2011)</ref><ref>Emacs-Has-Been-Violating-the-GPL-Since-2009 on slashdot.org (2011)</ref> Richard Stallman described this incident as ''"a very bad mistake"'',<ref>Re: Compiled files without sources???? Richard Stallman (28 Jul 2011)</ref> no lawsuit was filed for this violation.

Code licensed under several other licenses can be combined with a program under the GPL without conflict, as long as the combination of restrictions on the work as a whole does not put any additional restrictions beyond what GPL allows.The GNU General Public License v3.0 – GNU Project – Free Software Foundation (FSF) In addition to the regular terms of the GPL, there are additional restrictions and permissions one can apply:

# If a user wants to combine code licensed under different versions of GPL, then this is only allowed if the code with the older GPL version includes an "any later version" statement.[ ] For instance, the GPLv3 licensed GNU LibreDWG library can't be used anymore by LibreCAD and FreeCAD who have GPLv2 only dependencies.FSF Wastes Away Another "High Priority" Project LibreDWG drama: the end or the new beginning?

# Code licensed under LGPL is permitted to be linked with any other code no matter what license that code has,GNU Lesser General Public License v2.1 – GNU Project – Free Software Foundation (FSF) though the LGPL does add additional requirements for the combined work. LGPLv3 and GPLv2-only can thus commonly not be linked, as the combined Code work would add additional LGPLv3 requirements on top of the GPLv2-only licensed software. Code licensed under LGPLv2.x without the "any later version" statement can be relicensed if the whole combined work is licensed to GPLv2 or GPLv3.[ ]

FSF maintains a list[ ] of GPL-compatible (License compatibility) free software licensesFrequently Asked Questions about the GNU Licenses – What does it mean to say that two licenses are "compatible"? Frequently Asked Questions about the GNU Licenses – What does it mean to say a license is "compatible with the GPL?" with many of the most common free software licenses, such as the original MIT/X license (MIT License), the BSD license (in its current 3-clause form) and the Artistic License 2.0.Black Duck Open Source Resource Center

David A. Wheeler has advocated that free/open source software developers use only GPL-compatible licenses, because doing otherwise makes it difficult for others to participate and contribute code.Make Your Open Source Software GPL-Compatible. Or Else. As a specific example of license incompatibility, Sun Microsystems' ZFS cannot be included in the GPL-licensed Linux kernel, because it is licensed under the GPL-incompatible CDDL. Furthermore, ZFS is protected by patents, so distributing an independently developed GPL-ed implementation would still require Oracle's permission.<ref>Linux: ZFS, Licenses and Patents | KernelTrap </ref>

A number of businesses use multi-licensing to distribute a GPL version and sell a proprietary (proprietary software) license to companies wishing to combine the package with proprietary code, using dynamic linking or not. Examples of such companies include MySQL AB, Digia PLC (Qt framework (Qt (framework)), before 2011 from Nokia), Red Hat (Cygwin) and Riverbank Computing (PyQt). Other companies, like the Mozilla Foundation (products include Mozilla Application Suite, Mozilla Thunderbird and Mozilla Firefox), used multi-licensing to distribute versions under the GPL and some other open-source licenses.

It is possible to use the GPL for text documents instead of computer programs, or more generally for all kinds of media, if it is clear what constitutes the source code (defined as "the preferred form of the work for making changes in it").<ref>Free Software Foundation: Frequently Asked Questions about the GNU Licenses: Can I use the GPL for something other than software? . Retrieved 20 June 2009.</ref> For manuals and textbooks, though, the FSF recommends the GNU Free Documentation License (GFDL) instead, which it created for this purpose.<ref>GNU project: Frequently Asked Questions about the GNU Licenses: Why don't you use the GPL for manuals? . Retrieved 20 June 2009.</ref> Nevertheless, the Debian developers recommended (in a resolution adopted in 2006) to license documentation for their project under the GPL, because of the incompatibility of the GFDL with the GPL (text licensed under the GFDL cannot be incorporated into GPL software).Draft Debian Position Statement about the GNU Free Documentation License (GFDL) <ref name="debianresolution">Debian Project: Resolution: Why the GNU Free Documentation License is not suitable for Debian . Voted February–March 2006. Retrieved 20 June 2009.</ref> Also, the FLOSS Manuals foundation, an organization devoted to creating manuals for free software, decided to eschew the GFDL in favor of the GPL for its texts in 2007.<ref>FLOSS Manuals foundation: License Change 6 June 2007. Retrieved 20 June 2009.</ref>

If the GPL is used for fonts, any documents or images made with such fonts might also have to be distributed under the terms of the GPL. This is not the case in countries like the US and Canada where copyright law is inapplicable to the appearance of fonts, though program code inside a font file may still be covered—which can complicate font embedding (since the document could be considered 'linked' to the font). FSF provides an exception (GPL font exception) for cases where this is not desired.Font Licensing How does the GPL apply to fonts?

Historically, the GPL license family has been one of the most popular software licenses in the FOSS domain.<ref name="blackduck2015"/><ref name="wheeler1997"/><ref name="redhat2000"/><ref name="freecode2008"/><ref name="mattasay2011"/><ref name="blackduck2013"/>

A 1997 survey of MetaLab (Ibiblio), then the largest free software archive, showed that the GPL accounted for about half of the software licensed therein.[ ] Similarly, a 2000 survey of Red Hat Linux 7.1 found that 53% of the source code was licensed under the GPL.Estimating Linux's Size As of 2003<sup class="plainlinks noprint asof-tag update" style="display:none;">[//en.wikipedia.org/w/index.php?title=GNU_General_Public_License&action=edit &#91;update&#93;]</sup><nowiki/>Category:Articles containing potentially dated statements from 2003Category:All articles containing potentially dated statements, about 68% of all projects and 82.1% of the OSI certified licensed projects listed on SourceForge.net were from the GPL license family.SourceForge.net: Software Map As of August 2008<sup class="plainlinks noprint asof-tag update" style="display:none;">[//en.wikipedia.org/w/index.php?title=GNU_General_Public_License&action=edit &#91;update&#93;]</sup><nowiki/>Category:Articles containing potentially dated statements from August 2008Category:All articles containing potentially dated statements, the GPL family accounted for 70.9% of the 44,927 free software projects listed on Freecode.[ ]

After the release of the GPLv3 in June 2007, the acceptance and adoption of this new GPL version was heavily discussed;The Curse of Open Source License Proliferation several projects decided against upgrading. For instance the linux kernel,<ref name="linuxlicense"/><ref name="torvaldsgpl"/> MySQL,<ref>MySQL changes license to avoid GPLv3 on Computer business review online (January 04, 2007)</ref> BusyBox,Busy busy busybox Re: Move GPLv2 vs v3 fun... AdvFS,<ref name="PressRelease">Press release concerning the release of the AdvFS source code </ref> Blender (Blender (software)),What's up with DWG adoption in free software? and as also the VLC media player decided against adopting the GPLv3.VLC media player to remain under GNU GPL version 2

On the other hand in 2009, two years after the release of the GPLv3, Google open-source programs office manager Chris DiBona reported that the number of open-source projects licensed software that had moved to GPLv3 from GPLv2 was 50%, counting the projects hosted at Google Code.GPLv3 hits 50 percent adoption &#124; The Open Road - CNET News

In 2011, four years after the release of the GPLv3, 6.5% of all open-source license projects are GPLv3 while 42.5% are GPLv2 according to Black Duck Software data.<ref name="byfield2011"/><ref>GPL, copyleft use declining faster than ever on ITworld on December 16, 2011 by Brian Proffitt</ref> Following in 2011 ''451 Group'' analyst Matthew Aslett argued in a blog post that copyleft licenses went into decline and permissive licenses increased, based on statistics from Black Duck Software.GPL, copyleft use declining faster than ever - Data suggests a sharper rate of decline, which raises the question: why? On the continuing decline of the GPL Similarly, in February 2012 Jon Buys reported that among the top 50 projects on GitHub five projects were under a GPL license, including dual licensed and AGPL projects.<ref>The Top Licenses on Github on ostatic.com by Jon Buys (Feb. 07, 2012)</ref>

GPL usage statistic from 2009 to 2013 was extracted from Freecode data by Walter van Holst while analyzing license proliferation.<ref name="waltervanholst2013">License proliferation: a naive quantitative analysis on lwn.net ''"Walter van Holst is a legal consultant at the Dutch IT consulting company mitopics. .[...] Walter instead chose to use data from a software index, namely Freecode [...] Walter's 2009 data set consisted of 38,674 projects [...]The final column in the table shows the number of projects licensed under "any version of the GPL". In addition, Walter presented pie charts that showed the proportion of projects under various common licenses. Notable in those data sets was that, whereas in 2009 the proportion of projects licensed GPLv2-only and GPLv3 was respectively 3% and 2%, by 2013, those numbers had risen to 7% and 5%."''</ref>

{| class="wikitable sortable"

|+Usage of GPL family licenses in % on Freecode<ref name="waltervanholst2013"/>

|-

!2009

!2010

!2011

!2012

!2013

!2014-06-18<ref>tags letter g tagged as GPL family (including misnamed variants) 21000+100+3000+2000+400 of 47985 projects on freecode (2014-06-18 frozen)</ref><ref>About Freecode on freecode.com ''"The Freecode site has been moved to a static state effective June 18, 2014 due to low traffic levels and so that folks will focus on more useful endeavors than site upkeep."''</ref>

|-

|72% || 63% || 61% ||59% || 58% || approx. 54%

|}

In August 2013, according to Black Duck Software, the website's data show that the GPL license family is used by 54% of open-source projects, with a breakdown of the individual licenses shown in the following table.Top 20 licenses

However, a later study in 2013 showed that software licensed under the GPL license family has increased, and that even the data from Black Duck Software have shown a total increase of software projects licensed under GPL. The study used public information gathered from repositories of the Debian Project (Debian), and the study criticized Black Duck Software for not publishing their methodology used in collecting statistics.GPL use in Debian on the rise: study Daniel German, Professor in the Department of Computer Science at the University of Victoria in Canada, presented a talk in 2013 about the methodological challenges in determining which are the most widely used free software licenses, and showed how he could not replicate the result from Black Duck Software.Surveying open source licenses

In 2015 according to BlackDuck the GPLv2 lost its first position on the MIT license and is now second, the GPLv3 dropped to fourth place while the Apache license kept its third position.<ref name="blackduck2015"/>

{| class="wikitable sortable"

|+Usage of GPL family licenses in the FOSS domain in % according Black Duck Software

|-

! License

! 2008-05-08The Curse of Open Source License Proliferation

! 2009-03-11<ref>Top 20 Most Commonly Used Open Source Licenses Shaun Connolly, March 11, 2009</ref>

! 2011-11-22<ref name="byfield2011"/>

! 2013-08-12<ref name="blackduck2013"/>

! 2015-11-19Top 20 licenses

|-

| GPLv2

| 58.69%

| 52.2%

| 42.5%

| 33%

| 23%

|-

| GPLv3

| 1.64%

| 4.15%

| 6.5%

| 12%

| 9%

|-

| LGPL 2.1

| 11.39%

| 9.84%

| ?

| 6%

| 5%

|-

| LGPL 3.0

| ? (<0.64%)

| 0.37%

| ?

| 3%

| 2%

|-

| GPL family together

| 71.72% (+ <0.64%)

| 66.56%

| ?

| 54%

| 39%

|}

A March 2015 analysis of the GitHub repositories revealed for the GPL license family an usage percentage of approx. 25%.Open source license usage on GitHub.com

The GPL License is incompatible with many application digital distribution systems, like the Mac App Store, and certain other software distribution platforms (on smartphones as well as PCs). The problem lies in the right "To make a copy for your neighbour", as this right is violated by the integrated DRM-Systems made to prevent copying of paid software. Even if the application is free-as-in-beer in the App Store in question, it might result in a violation of that app store's terms.<ref name="autogenerated1">"The GPL, the App Store and You " on tuaw.com</ref>

Note that there is a distinction between an app ''store'', which sells DRM (Digital rights management)-restricted software under proprietary licenses, and the more general concept of digital distribution via some form of online software repository. Various UNIX-like distributions (Linux distribution) provide app repositories, including Fedora, RHEL, CentOS, Ubuntu (Ubuntu (operating system)), Debian, FreeBSD, OpenBSD and so on. These specific app repos all contain GPL-licensed software apps, in some cases even when the core project does not permit GPL-licensed code in the base system (for instance OpenBSD<ref name=openbsdpolicy>"Copyright Policy" , OpenBSD</ref>). In other cases, such as the Ubuntu App Store, proprietary commercial software applications ''and'' GPL-licensed applications are both available via the same system; the reason that the Mac App Store (and similar projects) is incompatible with GPL-licensed apps is not inherent in the concept of an app store, but is rather specifically due to Apple's terms-of-use requirement<ref name="autogenerated1"/> that all apps in the store utilize Apple DRM-restrictions. Ubuntu's app store does not demand any such requirement: "These terms do not limit or restrict your rights under any applicable open source software licenses."Ubuntu One : Terms and Conditions

In 2001, Microsoft CEO Steve Ballmer referred to Linux as "a cancer that attaches itself in an intellectual property sense to everything it touches".<ref>(Internet archive link)</ref><ref>text of GPL v1 with reference to source code download site at microsoft.com </ref> In response to Microsoft's attacks on the GPL, several prominent Free Software developers and advocates released a joint statement supporting the license.[ Free Software Leaders Stand Together] Microsoft has released Microsoft Windows Services for UNIX, which contains GPL-licensed code. In July 2009, Microsoft itself released a body of around 20,000 lines of Linux driver code under the GPL.[ ] The Hyper-V code that is part of the submitted code used open-source components licensed under the GPL and was originally statically linked to proprietary binary parts, the latter being inadmissible in GPL-licensed software.[ ]

The description of the GPL as "viral" (Viral license), when called 'General Public Virus' or 'GNU Public Virus' (GPV), dates back to a year after the GPLv1 was released.Re: Section 5.2 (IPR encumberance) in TAK rollover requirement draft General Public Virus Reverse-engineering the GNU Public Virus — Is copyleft too much of a good thing? Re: propose: `cypherpunks license' (Re: Wanted: Twofish source code) Re: Using of parse tree externally The GNU Public Virus

In 2001 the term received broader public attention when Craig Mundie, Microsoft Senior Vice President, described the GPL as being "viral".<ref>"Speech Transcript – Craig Mundie, The New York University Stern School of Business ", ''Prepared Text of Remarks by Craig Mundie'', Microsoft Senior Vice President, The Commercial Software Model The New York University Stern School of Business 3 May 2001</ref> Mundie argues that the GPL has a "viral" effect in that it only allows the conveyance of whole programs, which means programs that link (GPL linking exception) to GPL libraries must themselves be under a GPL-compatible license, else they cannot be combined and distributed.

In 2006 Richard Stallman responded in an interview that Mundie's metaphor of a "virus" is wrong as software under the GPL does not "attack" or "infect" other software. Stallman believes that comparing the GPL to a virus is an extremely unfriendly thing to say, and that a better metaphor for software under the GPL would be a spider plant (Chlorophytum comosum): If one takes a piece of it and puts it somewhere else, it grows there too.[ ][ ][ ]

On the other hand, the concept of a viral nature of the GPL was taken up by others later too.Comparative merits of GPL, BSD and Artistic licences (Critique of Viral Nature of GPL v.2 - or In Defense of Dual Licensing Idea) Some rights reserved: the alternatives to copyright (Wired UK) Glossary Inoculating Your Purchase – Contractual Protection from Viral Licenses in M&A Transactions <ref> </ref> For instance in 2008 the California Western School of Law characterized the GPL as: ''"The GPL license is ‘viral,’ meaning any derivative work you create containing even the smallest portion of the previously GPL licensed software must also be licensed under the GPL license"''.Open Source Licensing Guide

The FreeBSD project has stated that ''"a less publicized and unintended use of the GPL is that it is very favorable to large companies that want to undercut software companies. In other words, the GPL is well suited for use as a marketing weapon, potentially reducing overall economic benefit and contributing to monopolistic behavior"'' and that the GPL can ''"present a real problem for those wishing to commercialize and profit from software"''.GPL Advantages and Disadvantages

Richard Stallman wrote about the practice of selling license exceptions to free software licenses as an example of ethically acceptable commercialization practice. Selling exceptions here means that the copyright holder of a given software releases it (along with the corresponding source code) to the public under a free software license, "then lets customers pay for permission to use the same code under different terms, for instance allowing its inclusion in proprietary applications". Stallman considered selling exceptions "acceptable since the 1990s, and on occasion I've suggested it to companies. Sometimes this approach has made it possible for important programs to become free software". Despite that the FSF doesn't practice selling exceptions, a comparison with the X11 license (which is a non-copyleft free software license) is proposed for suggesting that this commercialization technique should be regarded as ethically acceptable. Releasing a given program under a noncopyleft free software license would permit embedding the code in proprietary software. Stallman comments that "either we have to conclude that it's wrong to release anything under the X11 license—a conclusion I find unacceptably extreme—or reject this implication. Using a noncopyleft license is weak, and usually an inferior choice, but it's not wrong. In other words, selling exceptions permits some embedding in proprietary software, and the X11 license permits even more embedding. If this doesn't make the X11 license unacceptable, it doesn't make selling exceptions unacceptable".<ref>Richard Stallman (2010). On Selling Exceptions to the GNU GPL . Free Software Foundation.</ref>

In 2000 developer and author Nikolai Bezroukov published an analysis and comprehensive critique of GPL's foundations and Stallman's (Richard Stallman) software development model, called "Labyrinth of Software Freedom".<ref>Bezroukov, Labyrinth of Software Freedom - "BSD vs GPL and social aspects of free licensing debate" on softpanorama.org by Nikolai Bezroukov Accessed 23 September 2010.</ref><ref>The Scope of Open Source Licensing - Harvard University by Josh Lerner and Jean Tirole (2002)</ref>

In 2005, open source software advocate Eric S. Raymond questioned the relevance of GPL at that point in time for the FOSS ecosystem, stating: "We don't need the GPL anymore. It's based on the belief that open source software is weak and needs to be protected. Open source would be succeeding faster if the GPL didn't make lots of people nervous about adopting it.".ESR: "We Don't Need the GPL Anymore" Richard Stallman replied that: "GPL ensure that every user of a program gets the essential freedoms--to run it, to study and change the source code, to redistribute copies, and to publish modified versions... [Raymond] addresses the issue in terms of different goals and values--those of "open source," which do not include defending software users' freedom to share and change software."RMS: The GNU GPL Is Here to Stay

In 2007 Allison Randal, who took part in the GPL draft committee, criticized the GPLv3 for being incompatible (License compatibility) with the GPLv2 and for missing clarity in the formulation.

In 2009 David Chisnall described in an InformIT article, ''"The Failure of the GPL"'', the problems with the GPL, among them incompatibility and complexity of the license text.The Failure of the GPL

In 2014 dtrace developer and Joyent CTO (Chief Technical Officer) Bryan Cantrill called the copyleft GPL a "Corporate Open Source Anti-pattern" by being "anti-collaborative" and recommended instead permissive (Permissive license) software licenses.Corporate Open Source Anti-patterns

Already in September 2006, in the draft process of the GPLv3, several high-profile developers of the Linux kernel, for instance Linus Torvalds, Greg Kroah-Hartman and Andrew Morton (Andrew Morton (computer programmer)), warned on a splitting of the FOSS community: ''"the release of GPLv3 portends the Balkanisation of the entire Open Source Universe upon which we rely."''.<ref name="kerneldevelopers2006"/>

Similarly Benjamin Mako Hill argued in 2006 on the GPLv3 draft, noting that an united, collaborating community is more important than a single license.Notes on the GPLv3

Following the GPLv3 release in 2007, some journalistsTorvalds Still Keen On GPLv2 7 Reasons Why Free Software Is Losing Influence: Page 2 Linux Creator Calls GPLv3 Authors 'Hypocrites' As Open Source Debate Turns Nasty and Toybox developer Rob Landley<ref name="landley2013"/> criticized that with the introduction of the GPLv3 the split between the open source and free software community became wider than ever. As the significantly extended GPLv3 is essentially incompatible (License compatibility) with the GPLv2,<ref name="gpl2gpl3comp"/> compatibility between both is only given under the optional ''"or later"'' clause of the GPL, which was not taken for instance by the Linux kernel.<ref name="linuxlicense"/> Bruce Byfield noted that before the release of the GPLv3, the GPLv2 was a unifying element between the open-source and the free software community.<ref name="byfield2011"/>

For the LGPLv3, GNU TLS maintainer Nikos Mavrogiannopoulos similarly argued, "If we assume that its [the LGPLv3] primary goal is to be used by free software, then it blatantly fails that.",The perils of LGPLv3 after he re-licensed ''GNU LTS'' from LGPLv3 back to LGPLv2.1 due to license compatibility issues.<ref>2013-03-14 Nikos Mavrogiannopoulos (nmav@gnutls.org) * COPYING.LESSER, README: gnutls 3.1.10 is LGPLv2.1 </ref><ref></ref>

Lawrence Rosen (Lawrence Rosen (attorney)), attorney and computer specialist, praised in 2007 how the community using the Apache license were now able to work together with the GPL community in a compatible manner, as the problems of GPLv2 compatibility with Apache licensed software were resolved with the GPLv3. He said, ''"I predict that one of the biggest success stories of GPLv3 will be the realization that the entire universe of free and open source software can thus be combined into comprehensive open source solutions for customers worldwide."''Comments on GPLv3

In July 2013 Flask (Flask (web framework)) developer Armin Ronacher draw a less optimistic resume on the GPL compatibility in the FOSS ecosystem when he concluded:''"When the GPL is involved the complexities of licensing becomes a non fun version of a riddle."'', also noting that the ASL 2.0 GPLv2 conflict still has impact on the ecosystem.Licensing in a Post Copyright World <ref>Are you sure you want to use the GPL? by Armin Ronacher (2009)</ref>

* Anti-copyright

* Dual-licensing

* European Union Public Licence (EUPL)

* GPL font exception

* List of software licenses

* Permissive and copyleft licenses