Python

Details

The project is provided under a PSF License Version 2, but used to have a complex licensing history before eventually settling for this license in 2001:

• Versions 0.9 through 1.2 (1991-1995) are provided under a CWI license agreement. The license for versions 1.3 through 1.5 (1995-1999) is identical except for the fact that it also mentions CNRI, which took over the development of Python in 1995.
• Version 1.6 (September 2000) is provided under a CNRI open source license agreement, which adds a choice of law clause stating that “this License Agreement shall be governed by and interpreted in all respects by the law of the State of Virginia”, and the release page has the following license guidance:

CNRI has placed an open source license on this version. CNRI believes that this version is compatible with the GPL, but there is a technicality concerning the choice of law provision, which Richard Stallman believes may make it incompatible. CNRI is still trying to work this out with Stallman. Future versions of Python will be released under a GPL-compatible license if at all possible.

• Version 2.0 (October 2000) is provided under a BeOpen Python open source license agreement version 1, which has the same choice of law clause, but with the state of California rather than Virginia.
• Version 1.6.1 (2001), which was deemed a “bugfix release” undergoing “the first step towards solving the GPL incompatibility”, is provided under a Python 1.6.1 license agreement, which modifies the choice of law clause so that incorporating code distributed under a GPL license in a derivative work of Python is not governed by the law of Virginia. The license guidance on the release page says the following:

Note: according to CNRI, Python 1.6.1 is GPL-compatible, but the FSF’s lawyer, has said that Python 1.6.1 is not compatible with the GPL. CNRI disagrees, and states the FSF’s lawyer has told CNRI’s lawyer that 1.6.1 is “not incompatible” with the GPL.

• Version 2.1 (April 2001) is provided under a PSF license agreement, which is identical to the 1.6.1 license but replaces CNRI with PSF. Following this release, its creator received an e-mail from the FSF asking them to remove the choice of law clause in order for the license to be considered GPL-compatible.
• Versions 2.0.1 (June 2001), 2.1.1 (July 2001) and all later versions are provided under a PSF License Version 2, which removes the choice of law clause as suggested by the FSF.

The project is run by the Python Software Foundation, a non-profit registered in the USA. According to its 2024 tax report, the PSF had that year a total income of 4.1 million dollars, of which 67% are membership fees, donations and grants, and 28% are PyCon US 2025 registration fees.