PSFL

PSFL stands for the Python Software Foundation License, a permissive open-source software license authored by the Python Software Foundation (PSF). It is used for Python's reference implementation and many related projects within the Python ecosystem. The license is designed to be straightforward and permissive, allowing wide redistribution and use in both open-source and proprietary software.

Key permissions under the PSFL include the rights to use, copy, modify, and distribute the software in source or binary form, including for commercial purposes. It permits sublicensing and the distribution of derivative works. The main conditions require that copyright notices and the license text be preserved in all copies or substantial portions of the software, and that a disclaimer of warranty be retained. If you modify the files, you should document the changes in a manner consistent with the license terms.

The PSFL also places restrictions, notably that the name of the Python Software Foundation or the contributors cannot be used to endorse or promote products derived from the software without permission. The license does not grant trademark rights, so branding and marketing claims may require separate permissions.

In terms of status, the PSFL is an OSI-approved permissive license and is widely used in the Python ecosystem. It is generally considered compatible with many other licenses, although project admins should evaluate license compatibility when combining PSFL-licensed code with code under copyleft licenses.

History and usage notes: the PSFL was created to provide a practical, permissive license for Python-related software, and it remains the standard license for Python core components and many third-party projects.