Microsoft Public License
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| Microsoft Public License | |
|---|---|
| Name | Microsoft Public License |
| Abbrev | Ms-PL |
| Author | Microsoft Corporation |
| Linking | Permissive |
| Date | 2006 |
Microsoft Public License
The Microsoft Public License is a permissive software license published by Microsoft Corporation in 2006. It grants broad rights to use, modify, and distribute covered source code while imposing minimal restrictions compared with copyleft terms found in some open-source instruments. The license occupies a role among contemporary permissive licenses alongside texts like the MIT License, Apache License 2.0, and the BSD licenses in projects connected to .NET Framework, NuGet, and other Microsoft ecosystems.
History and development
The Microsoft Public License emerged in a period when Microsoft Corporation sought to engage more directly with the open-source software community and the broader software development ecosystem. Announced in 2006, the license followed earlier initiatives including Shared Source Initiative releases and predated later moves such as the release of .NET Core under the MIT License. Key figures in the timeline include teams within Microsoft Research and product groups responsible for Windows and Visual Studio tooling. The license's creation coincided with wider community shifts sparked by events like the proliferation of GitHub and the adoption patterns shaped by entities such as Google, IBM, and Red Hat.
During its development, the license was positioned as a clear, concise permissive option intended to reduce legal friction for contributors and downstream users. It was published at a time when debates among stakeholders including Open Source Initiative, Free Software Foundation, and corporate legal departments over compatibility and patent terms were active. The license design reflects considerations similar to those in licenses used by projects at Microsoft Research, Outercurve Foundation, and other collaborative ventures.
Terms and conditions
The license grants recipients rights to reproduce, prepare derivative works, and distribute the covered code, subject to a few explicit requirements. It requires preservation of copyright notices and a copy of the license with any distribution of substantial portions of the code. The license also disclaims warranties and limits liability, mirroring standard formulations found in other permissive licenses.
Notably, the text does not include a broad patent grant comparable to the express patent license present in the Apache License 2.0. This difference has practical implications for contributors and downstream implementers, as discussions about patent scope have involved stakeholders from organizations such as Intel Corporation, Qualcomm, and Samsung Electronics. The document allows sublicensing and commercial use, facilitating incorporation into proprietary products from companies like Dell Technologies, HP, and Oracle Corporation.
The license is short and deliberately readable to appeal to engineering teams and legal counsels in corporations such as Accenture, Capgemini, and Tata Consultancy Services. Its permissive nature supports linking with code under other licenses including the MIT License and certain BSD variants, while requiring attention when combining with copyleft licenses like the GNU General Public License used by projects at Free Software Foundation.
Compatibility and adoption
Adoption of the license has been evident in several Microsoft-adjacent projects and in third-party repositories hosted on services like GitHub and Bitbucket. It has been accepted by the Open Source Initiative, which facilitated corporate usage and inclusion in package ecosystems such as NuGet and npm where cross-licensing interplay with Node.js packages and JavaScript libraries occurs.
Some organizations favored other permissive licenses with explicit patent clauses, such as the Apache License 2.0, especially after open-source projects from Google and Facebook influenced industry norms. Nevertheless, the license remains in use for projects that prioritize minimal obligations, including components in Mono, elements of tooling for Visual Studio Code extensions, and libraries distributed via Chocolatey and MSYS2.
Compatibility conversations have involved large foundations and consortia, including Linux Foundation, Eclipse Foundation, and OpenStack Foundation, as these entities assess how permissive licenses interact with contributor agreements and governance models. The license's permissive stance has eased commercial adoption by firms like Amazon Web Services, Microsoft Azure, and IBM Cloud when integrating small libraries.
Legal considerations and criticisms
Legal commentators and counsel have noted the license's brevity as both an advantage and a drawback. The absence of an explicit patent license clause has drawn scrutiny from legal teams at companies such as Google, Apple Inc., and Amazon.com, Inc., who often prefer explicit patent covenants to reduce litigation risk. Critics in the free software community, including voices associated with the Free Software Foundation, have pointed to potential ambiguities in patent scope and downstream obligations.
Litigation history explicitly tied to the license is limited; however, broader patent disputes in the software industry involving entities like Microsoft Corporation and Motorola Mobility have influenced perceptions of licenses lacking express patent provisions. Legal practitioners in firms such as Baker McKenzie, DLA Piper, and Skadden, Arps, Slate, Meagher & Flom frequently advise clients to evaluate license choice in the context of corporate patent portfolios and contributor practices.
Some open-source governance experts recommend pairing the license with contributor license agreements or using alternative permissive licenses with clearer patent language to align with policies adopted by consortia like the Linux Foundation.
Implementations and notable projects
Notable projects and implementations that have used the license include components contributed by Microsoft Research and smaller libraries distributed alongside .NET Framework reference implementations. Third-party projects on platforms such as GitHub and SourceForge have applied the license for utilities, UI controls, and developer tooling.
Uses in cross-platform initiatives like Mono and integrations with package managers such as NuGet have demonstrated the license's role in facilitating reuse across proprietary and open-source stacks. Smaller companies and independent maintainers, including those collaborating with organizations like Outercurve Foundation and participating in events such as Microsoft Build and Open Source Summit, have chosen the license for its simplicity.