BSD 2-Clause

BSD 2-Clause
Name	BSD 2-Clause
Other names	Simplified BSD License, FreeBSD License
Author	University of California, Berkeley
Date	1999
Header	Redistribution and use...

BSD 2-Clause is a permissive free software license originating from the Berkeley Software Distribution lineage associated with the University of California, Berkeley and its Computer Systems Research Group. It reduces the original BSD license language to two primary obligations and is widely used by projects such as FreeBSD, OpenBSD, NetBSD, PostgreSQL, and LLVM. The license is favored in industry and academia for its minimal restrictions, enabling adoption by organizations including IBM, Microsoft, Google, Apple Inc., and Red Hat.

History

The two-clause text evolved from the earlier four-clause BSD license that included an advertising clause tied to the University of California and corporate contributors. After debates within the Free Software Foundation and the Open Source Initiative, contributors and maintainers including developers from Keith Bostic-led teams at the Computer Systems Research Group removed the advertising requirement to resolve compatibility issues with licenses such as the GNU General Public License and to address concerns raised by entities like Sun Microsystems and AT&T Corporation. The simplified form gained traction during the 1990s and 2000s among projects like FreeBSD, NetBSD, OpenBSD, Darwin (operating system), and partly influenced permissive licensing choices at Mozilla Foundation and Eclipse Foundation-affiliated efforts.

License Text

The canonical two-clause wording appears in distributions from University of California, Berkeley maintainers and has been incorporated into repositories for FreeBSD, NetBSD, and OpenBSD. It consists of a short preamble granting permission for redistribution and use, followed by two numbered clauses specifying: preservation of copyright notice and disclaimer of warranty. Implementations of the license have been published by projects and organizations such as Debian Project, Open Source Initiative, and Software Freedom Law Center for clarity and guidance, and variations appear in codebases from Apple Inc.'s Darwin (operating system), Google open-source projects, and The Apache Software Foundation-hosted mirrors.

Terms and Conditions

The primary obligations require that redistributions of source code retain the original copyright notice and license text, and redistributions in binary form reproduce the notice and disclaimer in documentation or other materials provided with the distribution. The license explicitly disclaims warranties and limits liability, aligning with protections used by entities like IBM, Microsoft, and Oracle Corporation to mitigate legal exposure. Because it imposes minimal restrictions, maintainers from projects such as PostgreSQL, SQLite, and LLVM choose it to permit proprietary relicensing, commercial use, and combination with permissive and proprietary codebases, a practice also seen at companies like Nokia and Cisco Systems.

Compatibility and Use

The two-clause text is compatible with the GNU General Public License for certain versions and has been evaluated in compatibility discussions involving Free Software Foundation policy, the Open Source Initiative, and distributions like Debian Project and Ubuntu (operating system). Major kernel and system projects including FreeBSD, NetBSD, and OpenBSD use or accept this license for contributions, and large corporations including Apple Inc. and Google accept it for internal and public releases. Its permissive nature allows incorporation into proprietary products from Microsoft and Oracle Corporation, as well as permissive aggregation with code under MIT License or Apache License terms, though compatibility with patent-related clauses from Apache Software Foundation has been a topic in joint licensing decisions involving Eclipse Foundation and Linux Foundation projects.

Legal Interpretation and Case Law

While the BSD two-clause license has seen less dedicated litigation than copyleft licenses, its warranty disclaimer and liability limitation language have been analyzed by legal teams at institutions such as University of California, Berkeley, Software Freedom Law Center, and law firms advising Red Hat and Canonical (company). Interpretations by counsel for corporations like IBM, Microsoft, and Google have shaped practical enforcement approaches, and the license has been cited in compliance guidance from organizations such as the Open Source Initiative and European Commission-backed studies on open-source licensing. Disputes over attribution and redistribution practices have occasionally arisen in contexts involving companies like Sony Corporation and Samsung Electronics, but rarely culminated in high-profile court rulings analogous to cases involving SCO Group or Oracle Corporation.

Reception and Criticism

Advocates from FreeBSD, NetBSD, and corporate adopters like IBM and Google praise the two-clause wording for simplicity and business friendliness, arguing it facilitates widespread reuse by projects and corporations including Apple Inc. and Microsoft. Critics from segments of the Free Software Foundation and some contributors to GNU Project and Debian Project prefer stronger copyleft terms as found in the GNU General Public License to ensure downstream freedom, citing philosophical differences echoed in debates involving Richard Stallman and Linus Torvalds. Others note that permissive relicensing enabled by the two-clause license has allowed incorporation into proprietary offerings by companies such as Microsoft, Apple Inc., and Amazon (company), drawing mixed commentary from the Open Source Initiative community and academic commentators at institutions like Massachusetts Institute of Technology and Stanford University.

Category:Software licenses