Python Software Foundation License

Python Software Foundation License
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Name	Python Software Foundation License
Author	Python Software Foundation
Version	2.0
Copyright	Python Software Foundation
Published	2001
Copyleft	Permissive

Python Software Foundation License. The Python Software Foundation License is a permissive free software license authored and stewarded by the Python Software Foundation. It is the official license for the Python (programming language) interpreter and its standard library, granting broad freedoms for use, modification, and distribution. The license is approved by the Open Source Initiative and the Free Software Foundation, ensuring its alignment with core open-source software principles.

History and development

The license's origins are tied to the early stewardship of Guido van Rossum, the creator of Python, and the Corporation for National Research Initiatives, which held the initial copyright. Following the establishment of the Python Software Foundation in 2001, the license was formally adopted to govern the language's reference implementation. This transition marked a pivotal shift from earlier licensing models, such as the Python License and the CNRI Python License, consolidating control under a dedicated non-profit entity. The move was influenced by broader trends in the free software movement and aimed to provide unambiguous, modern terms for a growing global community of developers and corporations like Google and Microsoft.

License terms and conditions

The license grants recipients permission to use, copy, modify, and distribute the software and its source code, with or without modification. Key conditions include retaining all original copyright, permission, and disclaimer notices from the Python Software Foundation. The text includes a standard disclaimer of warranty, absolving the Python Software Foundation and contributors from liability, a common clause in licenses like the BSD licenses. Unlike copyleft licenses such as the GNU General Public License, it does not require derivative works to be distributed under the same terms, allowing integration into proprietary products. The license is expressly designed to be compatible with the GNU General Public License, facilitating its use in projects like those hosted on GitHub.

Compatibility with other licenses

The Python Software Foundation License is explicitly compatible with the GNU General Public License, a status formally recognized by the Free Software Foundation. This compatibility allows code under this license to be combined with or incorporated into projects governed by the GNU General Public License version 3.0, a feature critical for its adoption in the Linux ecosystem and projects like Fedora (operating system). Its permissive nature also ensures compatibility with other major licenses, including the Apache License, MIT License, and BSD licenses, enabling flexible reuse across the open-source landscape. This interoperability is a significant factor in its endorsement by organizations such as the Apache Software Foundation and its use in diverse environments from NASA to Netflix.

Usage and adoption

Primary usage is for the official CPython interpreter, the standard library, and related documentation maintained by the Python Software Foundation. The license's permissiveness has led to widespread adoption by major technology firms, including Instagram, Spotify, and Dropbox (service), for both internal tools and public-facing services. It is also the license for critical components in scientific computing, such as the reference implementations used with NumPy and parts of the SciPy ecosystem. The license's terms support its inclusion in commercial products and operating systems like macOS and distributions from Red Hat, cementing Python's role in enterprises and academia from CERN to MIT.

Comparison with other open-source licenses

Compared to strong copyleft licenses like the GNU General Public License or the GNU Affero General Public License, it imposes far fewer redistribution obligations, making it more attractive for commercial integration. Unlike the Apache License 2.0, it does not include an explicit patent grant clause, though it maintains a similar permissive stance on contributions. Its simplicity and brevity are often compared to the MIT License, though it is uniquely tailored to the governance structure of the Python Software Foundation. When contrasted with the original BSD licenses, it offers more modern and clear language regarding license compatibility, particularly with the GNU General Public License, as affirmed by the Free Software Foundation.

Category:Free software licenses Category:Python Software Foundation