Software relicensing is applied in open-source software development when software licenses of software modules are incompatible and are required to be compatible for a greater combined work. Licenses applied to software as copyrightable works, in source code as binary form, can contain contradictory clauses. These requirements can make it impossible to combine source code or content of several software works to create a new combined one.
Motivation and description
Sometimes open-source software projects get stuck in a license incompatibility situation. Often the only feasible way to resolve this situation is re-licensing of all participating software parts. For successful relicensing the agreement of all involved copyright holders, typically the developers, to a changed license is required. While in the free and open-source domain achieving 100% coverage of all authors is often impossible due to the many contributors involved, often it is assumed that a great majority is sufficient. For instance, Mozilla assumed an author coverage of 95% to be sufficient. Others in the free and open-source software (FOSS) domain, such as Eric S. Raymond, came to different conclusions regarding the requirements for relicensing of a whole code base.
An early example of an open-source project that did successfully re-license for license compatibility reasons is the Mozilla project and their Firefox browser. The source code of Netscape's Communicator 4.0 browser was originally released in 1998 under the Netscape Public License/Mozilla Public License but was criticised by the FSF and OSI for being incompatible. Around 2001 Time Warner, exercising its rights under the Netscape Public License, and at the request of the Mozilla Foundation, relicensed all code in Mozilla that was under the Netscape Public License (including code by other contributors) to an MPL 1.1/GPL 2.0/LGPL 2.1 tri-license, thus achieving GPL-compatibility.
The VLC project also has a complicated license history due to license compatibility: in 2007 it decided for license compatibility reasons to not upgrade to the just released GPLv3. After the VLC was removed from Apple App Store at the beginning of 2011, in October 2011 the VLC project re-licensed the VLC library part from the GPLv2 to the LGPLv2 to achieve better compatibility. In July 2013 the VLC application could then be resubmitted to the iOS App Store relicensed under the Mozilla Public License.
7-Zip's LZMA SDK, originally dual-licensed under both the GNU LGPL and Common Public License, with an additional special exception for linked binaries, was placed by Igor Pavlov in the public domain on December 2, 2008.
The GNU Free Documentation License in version 1.2 is not compatible with the widely used Creative Commons Attribution-ShareAlike license, which was a problem, for instance, for the Wikipedia. Therefore, at the request of the Wikimedia Foundation, the FSF added, with version 1.3 of the GFDL, a time-limited section allowing specific types of websites using the GFDL to additionally offer their work under the CC BY-SA license. Following in June 2009, the Wikimedia Foundation migrated their projects (Wikipedia, etc.) by dual licensing to the Creative Commons Attribution-ShareAlike as main license, additional to the previously used GFDL. An improved license compatibility with the greater free content ecosystem was given as reason for the license change.
Another case was the relicensing of GPLv2 licensed linux kernel header files to the BSD license by Google for their Android library Bionic. To get rid of the GPL, Google claimed that the header files were cleaned from any copyright-able work, reducing them to non-copyrightable "facts". This interpretation was challenged for instance by Raymond Nimmer, a law professor at the University of Houston Law Center.
In November 2013 POV-Ray was relicensed under the Affero General Public License version 3 (or later), after being distributed since 1991 under a FOSS-incompatible, non-commercial source available custom POV-Ray license. POV-Ray was developed before FOSS licenses became widely used, therefore the developers wrote their own license which became later a problem due to license incompatibility with the FOSS ecosystem.
In June 2015 mpv started the relicensation process of the project's GPL licensed source code for improved license compatibility under LGPLv2 by getting consent from the majority (95%+) of the contributing developers. In August 2016 approx. 90% of the authors could be reached and consented. In October 2017 the switch was finalized.
In August 2016 the MariaDB Corporation relicensed the database proxy server MaxScale from GPL to the non-FOSS but source-available and time-limited Business source license (BSL) which defaults back after three years to GPL. In 2017 followed version 1.1, revised with feedback also from Bruce Perens.
For a long time D back-end source code was available but under a non-open source conform license, because it was partially developed at Symantec and couldn't be relicensed as open source. On April 9, 2017, also the back-end part could be relicensed to the open-source Boost Software License.
On July 27, 2017 Microsoft Research changed the license of space combat simulator Allegiance from the MSR shared source license, under which the game was opened in 2004, to the MIT license.
- Hancock, Terry (2008-08-29). "What if copyright didn't apply to binary executables?". Free Software Magazine. Retrieved 2016-01-25.
- O'Riordan, Ciaran (2006-11-10). "How GPLv3 tackles license proliferation". linuxdevices.com. Archived from the original on 2007-12-18.
- Neary, Dave (February 15, 2012). "Gray areas in software licensing". lwn.net. Retrieved 2016-02-27.
- O’Riordan, Ciaran (2006-10-06). "(About GPLv3) Can the Linux Kernel Relicense?". fsfe.org. Retrieved 2015-05-28.
Someone who works with many lawyers on free software copyright issues later told me that it is not necessary to get permission from 100% of the copyright holders. It would suffice if there was permission from the copyright holders of 95% of the source code and no objections from the holders of the other 5%. This, I’m told, is how Mozilla was able to relicense to the GPL in 2003 despite years of community contributions.
- Licensing HOWTO by Eric Steven Raymond&Catherine Olanich Raymond "Changing an existing license [...]You can change the license on a piece of code under any of the following conditions: If you are the sole copyright holder[...]If you are the sole registered copyright holder[...] If you obtain the consent of all other copyright holders[...]If no other copyright holder could be harmed by the change" (accessed on 2015-11-21)
- Netscape Public License FAQ on mozilla.org
- "Licenses by Name - Open Source Initiative". Open Source Initiative. Retrieved 2014-08-27.
- On the Netscape Public License by Richard Stallman on GNU.org
- "Mozilla Relicensing FAQ Version 1.1". mozilla.org. Archived from the original on 2010-05-13.
Some time ago mozilla.org announced its intent to seek relicensing of Mozilla code under a new licensing scheme that would address perceived incompatibilities of the Mozilla Public License (MPL) with the GNU General Public License (GPL) and GNU Lesser General Public License (LGPL).
- Relicensing Complete on gerv.net by Gervase Markham (March 31, 2006)
- February 2001 on xiph.org "With the Beta 4 release, the Ogg Vorbis libraries have moved to the BSD license. The change from LGPL to BSD was made to enable the use of Ogg Vorbis in all forms of software and hardware. Jack Moffitt says, "We are changing the license in response to feedback from many parties. It has become clear to us that adoption of Ogg Vorbis will be accelerated even further by the use of a less restrictive license that is friendlier toward proprietary software and hardware systems. We want everyone to be able to use Ogg Vorbis.""
- RMS on license change on lwn.net
- Denis-Courmont, Rémi. "VLC media player to remain under GNU GPL version 2". videolan.org. Retrieved 2015-11-21.
In 2001, VLC was released under the OSI-approved GNU General Public version 2, with the commonly-offered option to use "any later version" thereof (though there was not any such later version at the time). Following the release by the Free Software Foundation (FSF) of the new version 3 of its GNU General Public License (GPL) on the 29th of June 2007, contributors to the VLC media player, and other software projects hosted at videolan.org, debated the possibility of updating the licensing terms for future version of the VLC media player and other hosted projects, to version 3 of the GPL. [...] There is strong concern that these new additional requirements might not match the industrial and economic reality of our time, especially in the market of consumer electronics. It is our belief that changing our licensing terms to GPL version 3 would currently not be in the best interest of our community as a whole. Consequently, we plan to keep distributing future versions of VLC media player under the terms of the GPL version 2. [...]we will continue to distribute the VLC media player source code under GPL "version 2 or any later version" until further notice.
- "Changing the VLC engine license to LGPL". Retrieved 23 October 2011.
- Vaughan-Nichols, Steven. "No GPL Apps for Apple's App Store". zdnet.com. Retrieved 23 October 2011.
- VLC under Mozilla public relaunched. on Ars Technica (Accessed 10/10/2013)
- "Browse /LZMA SDK/4.23". SourceForge. Retrieved 2014-02-12.
- Pavlov, Igor (2013). "LZMA SDK (Software Development Kit)". Retrieved 2013-06-16.
- Mavrogiannopoulos, Nikos (2013-03-26). "The perils of LGPLv3". gnutls.org. Retrieved 2015-11-18.
LGPLv3 is the latest version of the GNU Lesser General Public License. It follows the successful LGPLv2.1 license, and was released by Free Software Foundation as a counterpart to its GNU General Public License version 3. The goal of the GNU Lesser General Public Licenses is to provide software that can be used by both proprietary and free software. This goal has been successfully handled so far by LGPLv2.1, and there is a multitude of libraries using that license. Now we have LGPLv3 as the latest, and the question is how successful is LGPLv3 on this goal? In my opinion, very little. If we assume that its primary goal is to be used by free software, then it blatantly fails that.
- Version 2.99.4 (released 2011-07-23)[...] ** libgnutls: license upgraded to LGPLv3
- 2013-03-14 Nikos Mavrogiannopoulos (firstname.lastname@example.org) * COPYING.LESSER, README: gnutls 3.1.10 is LGPLv2.1
- "FDL 1.3 FAQ". Gnu.org. Retrieved 2011-11-07.
- "Resolution:Licensing update approval - Wikimedia Foundation".
- Wikipedia + CC BY-SA = Free Culture Win! on creativecommons.org by Mike Linksvayer, June 22nd, 2009
- Licensing update rolled out in all Wikimedia wikis on wikimedia.org by Erik Moeller on June 30th, 2009 "Perhaps the most significant reason to choose CC-BY-SA as our primary content license was to be compatible with many of the other admirable endeavors out there to share and develop free knowledge"
- Licensing FAQ on ogre3d.org
- My evolving view of open source licenses by Steve (2009/09/15)
- OGRE Will Switch To The MIT License from 1.7 on ogre3d.org by sinbad (Sep 15, 2009)
- Google android and the linux headers on theregister.com (2011)
- Android: Sued by Microsoft, not by Linux "Microsoft launches new Android suit, Linus Torvalds' take on Linux kernel headers and Android" on ITworld (March 21, 2011)
- Infringement and disclosure risk in development on copyleft platforms on ipinfoblog.com by Raymond Nimmer (2011)
- Cason, Chris (8 November 2013). "Download POV-Ray 3.7.0". Retrieved 11 November 2013.
Starting with version 3.7, POV-Ray is released under the AGPL3 (or later) license and thus is Free Software according to the FSF definition. […] Full source code is available, allowing users to build their own versions and for developers to incorporate portions or all of the POV-Ray source into their own software provided it is distributed under a compatible license (for example, the AGPL3 or – at their option – any later version).
- "POV-Ray 3.6 Distribution License". Povray.org. Retrieved 2016-12-12.
- "POV-Ray 3.6 Source License". Povray.org. Retrieved 2016-12-12.
- Prokoudine, Alexandre (2012-12-27). "LibreDWG drama: the end or the new beginning?". libregraphicsworld.org. Retrieved 2013-08-23.
[...]the unfortunate situation with support for DWG files in free CAD software via LibreDWG. We feel, by now it ought to be closed. We have the final answer from FSF. [...] "We are not going to change the license."
- "license". freecadweb.org. 2014. Retrieved 2015-03-25.
Licences used in FreeCAD - FreeCAD uses two different licenses, one for the application itself, and one for the documentation: Lesser General Public Licence, version 2 or superior (LGPL2+) […] Open Publication Licence
- "Gang-Garrison-2/License.txt". GitHub. 2014-11-09. Retrieved 2015-03-23.
- "Planned license change (GPL -> MPL), Help needed". Gang Garrison 2 Forums. 2014-08-23. Retrieved 2015-03-23.
tl;dr: The current license prevents us from using certain nice and (cost-)free libraries / frameworks, so we want to change it. The new license (MPL) would be strictly more free than the old one, and is the same one that's also used by Firefox.
- Relicensing Dolphin: The long road to GPLv2+ Written by JMC47, MaJoR on May 25, 2015
- Possible LGPL relicensing #2033 on github.com "GPL-incompatible dependencies such as OpenSSL are a big issue for library users, even if the library user is ok with the GPL."
- The LGPL relicensing is "official" now, and git master now has a --enable-lgpl configure option. by wm4 on github.com
- Why change Natron licence to GPL V2? Can you explain your motivation ? Why change from Mozilla to GPL ? on natron.fr MrKepzieLeader: "The main reasoning is that in the future there will be derivative work spun off Natron, and we want to be able to still control where our source code is going and who is selling it." (Aug 2015)
- MAME is now Free and Open Source Software on mamedev.org (March 4, 2016)
- the-already-dead-theory on mamedev.emulab.it
- So why did this annoy me so much? on mameworld.info (10/22/13)
- "10 months later, MAME finishes its transition to open source". Gamasutra. Retrieved 5 March 2016.
- "MAME is going open source to be a 'learning tool for developers'". Gamasutra. UBM plc. Retrieved 27 May 2015.
- bsl "Change Date: 2019-01-01, Change License: Version 2 or later of the GNU General Public License as published by the Free Software Foundation." on mariadb.com (August 2016)
- MySQL daddy Widenius: Open-source religion won't feed MariaDB on theregister.com (August 2016)
- A new release of the MaxScale database proxy -- essential to deploying MariaDB at scale -- features a proprietary license on InfoWorld by Simon Phipps (Aug 19, 2016)
- sl-1-1 on perens.com (2017-02-14)
- releasing-bsl-11 on mariadb.com by Kaj Arnö (2017)
- "backendlicense.txt". DMD source code. GitHub. Archived from the original on 22 October 2016. Retrieved 5 March 2012.
- "Reddit comment by Walter Bright". Retrieved 9 September 2014.
- D-Compiler-unter-freier-Lizenz on linux-magazin.de (2017, in German)
- "dmd Backend converted to Boost License". 7 April 2017. Retrieved 9 April 2017.
- switch backend to Boost License #6680 from Walter Bright on github.com
- allegiancelicense.txt Archived 7 November 2014 at the Wayback Machine Microsoft Research Shared Source license agreement ("MSR-SSLA")
- Colayco, Bob (2004-02-06). "Microsoft pledges Allegiance to its fanbase". gamespot.com. Archived from the original on 10 December 2013. Retrieved 2011-07-22.
- Horvitz, Eric (2017-07-28). "Allegiance Relicense Letter" (PDF). Director, Microsoft Research. Retrieved 2017-07-28.
Microsoft Corporation ("Microsoft") hereby relicenses the Microsoft Video Game Allegiance source code found at https://github.com/FreeAllegiance/Allegiance/tree/master/src ("Allegiance Source Code") from the current Microsoft Research Shared Source license Agreement (MSR-SSLA) to the MIT license.
- FREEING Allegiance, How it Happened (sort of) on freeallegiance.org (2017-07-28)