He advocated the use of the GPLv3 license, especially noting Linus Torvalds' refusal to switch away from GPLv2 for the Linux kernel.
Therefore, there was a strong controversy around the update of the GNU GPLv2 to the GNU GPLv3 in 2007, as the updated license is not compatible with the previous version.
However, works using the latter that have given permission to use a later version of the GPL are compatible: a work released under the GPLv2 "or any later version" may be combined with code from a LGPL version 3 library, with the combined work as a whole falling under the terms of the GPLv3.
Torvalds used Stallman's GNU General Public License version 2 (GPLv2) for his Linux kernel.
As of 2015, according to Black Duck Software and a 2015 blog from GitHub, the MIT license was the most popular free software license, with the GNU GPLv2 coming second in their sample of repositories.
The kernel source and proofs are under GPLv2, and most libraries and tools are under the 2-clause BSD license.
The source code of Strife: Veteran Edition was made available under GPLv2 on github.com.
As of 2015, according to Black Duck Software and GitHub, the Apache license is the third most popular license in the FOSS domain after MIT license and GPLv2.
In September 2010, a company named "Applidium" developed a VLC port for iOS under GPLv2 with the endorsement of the VLC project, which was accepted by Apple for their App Store.
In January 2011, after VLC developer Rémi Denis-Courmont's complaint to Apple about the licensing conflict between the VLC's GPLv2 and the App store's policies, the VLC had been withdrawn from the Apple App Store by Apple.
Subsequently, in October 2011 the VLC authors began to relicense the engine parts of VLC from the GPLv2 to the LGPLv2 to achieve better license compatibility, for instance with the Apple App Store.