2-clause BSD license

2-clause BSD license
Name	2-clause BSD license
Othernames	FreeBSD License, Simplified BSD License
Issued	1999
Long	Permissive free software license

2-clause BSD license is a permissive free software license originating from the University of California, Berkeley. It simplifies earlier permissive terms to two primary conditions, encouraging reuse by corporations, projects, and governments while retaining a minimal attribution requirement. The license has influenced a broad range of projects, institutions, and interoperability debates across the software ecosystem.

History

The 2-clause BSD license descends from the Berkeley Software Distribution lineage associated with University of California, Berkeley, William Keith-era networking work, and the redistribution practices formalized in the late 20th century. Its evolution traces through legal and cultural shifts involving actors such as Robert Tappan Morris, Keith Bostic, Marshall Kirk McKusick, and organizations including FreeBSD Project, NetBSD Foundation, and OpenBSD Project. Corporate and institutional adopters influenced its shape, including Apple Inc., Microsoft, Google, IBM, Oracle Corporation, Intel Corporation, and Red Hat. Jurisprudential and licensing discussions involved entities like Electronic Frontier Foundation, Software Freedom Law Center, and Linux Foundation, while standards and compatibility conversations engaged IEEE, World Wide Web Consortium, Internet Engineering Task Force, and Open Source Initiative.

Text of the License

The canonical text presents two operative clauses: an attribution requirement and a disclaimer of warranty and liability. The simplified two-clause form follows the intent of earlier forms used in the 4.4BSD releases and replaced the advertising clause that had caused disputes involving parties such as AT&T, Novell, and later community debates connecting to projects like Mozilla Foundation and Apache Software Foundation. The textual economy made the license attractive to projects from SQLite Consortium to NetBSD Foundation derivatives, and to corporations such as Sun Microsystems and ARM Holdings that required minimal encumbrance on redistribution.

Key Terms and Obligations

Key obligations include retaining copyright notices and the disclaimer in redistributed source and binary forms; the license requires preservation of attribution to authors or organizations such as University of California, Berkeley and contributors like Keith Bostic where applicable. The warranty disclaimer limits liability for parties including distributors like Debian Project, Canonical Ltd., and SUSE, and protects upstream maintainers such as those at FreeBSD Project or companies like Intel Corporation from suit in many jurisdictions. The license imposes no copyleft reciprocity obligations unlike licenses adopted by Free Software Foundation, such as the GNU General Public License, and thus permits proprietary relicensing by commercial actors including Microsoft and Apple Inc..

Comparison with Other BSD Variants

Compared to the original multi-clause BSD variants, the two-clause form removes the advertising clause present in the historical license used during the 4.4BSD era, aligning it more closely with licenses used by Free Software Foundation-critic projects and permissive models like the MIT License and the Apache License family. The three-clause BSD license adds a non-endorsement clause similar to text seen in agreements involving Mozilla Foundation trademarks and projects led by entities such as Eclipse Foundation. Corporate audiences at Google, Facebook, and Amazon.com have favored the two-clause form for simpler compliance compared with the Creative Commons-style attribution requirements in other ecosystems.

Legal Interpretations and Litigation

Courts and counsel have analyzed the warranty disclaimer and attribution obligations in cases touching on software redistribution and derivative works, situating arguments alongside precedents such as disputes involving Oracle Corporation, Google, Sun Microsystems, and Apple Inc.. Legal analysis by firms and organizations including Morrison & Foerster, Latham & Watkins, WilmerHale, Software Freedom Law Center, and bar associations in jurisdictions like United States federal courts and United Kingdom tribunals has focused on enforceability of disclaimers and the license's interaction with statutory warranties. International adoption prompted interpretation questions in bodies like the European Court of Justice context and regulatory offices in Canada and Australia when governments such as Government of the United Kingdom and agencies in European Union member states integrated BSD-licensed software.

Use and Adoption in Software Projects

The two-clause BSD license has been adopted by numerous prominent projects and institutions, including operating system projects like FreeBSD Project, NetBSD, and OpenBSD Project forks, tooling such as rsync, OpenSSH, LibreSSL derivatives, and libraries like libc variants and musl libc-adjacent works. Databases and embedded stacks such as SQLite and commercial offerings from Arm Ltd. and Nokia-era projects have utilized the license for permissive distribution. Major cloud and platform providers including Amazon Web Services, Google Cloud Platform, Microsoft Azure, and IBM Cloud host and redistribute BSD-licensed artifacts, while distribution ecosystems like Debian Project, Fedora Project, and Arch Linux manage compliance policies for such licenses.

Compatibility with Other Licenses

The two-clause BSD license is widely considered compatible with permissive and copyleft licenses for incorporation into larger works, enabling combination with projects under MIT License, ISC License, and many GPL-licensed codebases, subject to the version-specific terms of the GNU General Public License and provenance obligations enforced by maintainers at organizations like Free Software Foundation and Software Freedom Conservancy. Commercial relicense and dual-licensing strategies used by firms such as Red Hat, Oracle Corporation, and SUSE exploit this compatibility to distribute derivative or combined works under alternative terms, while foundations like Apache Software Foundation provide guidance on compatibility with patents and contributor agreements.

Category:Software licenses