Version 2 of the GNU General Public License (GPLv2) was released in June 1991. According to Richard Stallman, the major change in GPLv2 was the Liberty or Death clause, as he calls it in Section 7.
This section says that if a license imposes restrictions that ''prevent'' distributing GPL - covered software in a way that respects other users' freedom (for example, if a legal ruling states that someone may only distribute the software in binary form), the developer may not distribute it at all.
The hope is, that this makes it less tempting for companies to use patent threats to require fees from free software developers.
By 1990, it was becoming apparent that a less restrictive license would be strategically useful for the C library and for software libraries that essentially did the job of existing proprietary ones - gnu.org 
When version 2 of the GPL (GPLv2) was released in June 1991, therefore, a second license – the GNU Lesser General Public License or Library General Public License (LGPL) – was introduced at the same time and numbered with version 2 to show that both were complementary.
The version numbers diverged in 1999 when version 2.1 of the LGPL was released, which renamed it the GNU Lesser General Public License to reflect its place in the philosophy.