Copyright

.NET is a member project of the .NET Foundation.

Source copyright is held by ".NET Foundation and Contributors", while binary distributions (and associated copyright) are provided by a variety of parties.

Source License

The .NET project primarily uses the MIT License for code and Creative Commons licenses for non-code assets, like documentation, swag, and brand content.

We use the following approach for code contributions:

New code is licensed as MIT, per repo license and via file headers.
Contributions (like ports) can be based on existing code or algorithms that are licensed with a permissive OSI-approved licenses (for example, MIT, Apache 2, and BSD) and should be ackowledged in the repo THIRD-PARTY-NOTICE file.
Non-product contributions (like tests) can be based on existing code or algorithms that are licensed with any OSI-approved license (including GPL) and should be acknowleged in a local THIRD-PARTY-NOTICE file (for example, SciMark/THIRD-PARTY-NOTICES).
We will typically reject the use of product code licensed with Creative Commons or public domain licenses given their lack of universal acceptance.
The .NET Foundation Contribution License Agreement (CLA) is used to license contributions from contributors.

More mechanical guidance is provided in CONTRIBUTING.md.

References:

Binary License

Microsoft distributes binary builds of .NET per the following description. Distributions from other parties may differ.

Binary archives, installers, packages, and containers are licensed as MIT (same as the .NET source license).
Windows-based distributions include closed-source assets, per License information for .NET on Windows

Patents

Microsoft has issued a Patent Promise for .NET Libraries and Runtime Components.