There are patent pledges and promises not to assert patents: https://msdn.microsoft.com/en-us/openspecifications https://msdn.microsoft.com/en-us/openspecificat

There are patent pledges and promises not to assert patents: https://msdn.microsoft.com/en-us/openspecifications https://msdn.microsoft.com/en-us/openspecifications Portions of .NET are under ECMA and ISO standards: https://en.wikipedia.org/wiki/Common_Language_Infrastructure#Standardization_and_licensing https://en.wikipedia.org/wiki/Common_Language_Infrastructure... I think the most important part is that the new cross-platform .NET core framework, CLR, and compiler (Roslyn) are under permissive open source licenses (MIT for fx and clr, Apache 2 for Roslyn). You can see licenses and patent pledges here: https://github.com/dotnet/ https://github.com/dotnet/ Disclaimers: 1. Microsoft employee until they notice I'm hanging out on hacker news instead of replying to e-mails and "fix the glitch". 2. Not that smart and definitely not a lawyer.