There are patent pledges and promises not to assert patents: <a href="https:&#x2F;&#x2F;msdn.microsoft.com&#x2F;en-us&#x2F;openspecifications" rel="nofollow">https:&#x2F;&#x2F;msdn.microsoft.com&#x2F;en-us&#x2F;openspecifications</a><p>Portions of .NET are under ECMA and ISO standards: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Common_Language_Infrastructure#Standardization_and_licensing" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Common_Language_Infrastructure...</a><p>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: <a href="https:&#x2F;&#x2F;github.com&#x2F;dotnet&#x2F;" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;dotnet&#x2F;</a><p>Disclaimers:<p>1. Microsoft employee until they notice I&#x27;m hanging out on hacker news instead of replying to e-mails and &quot;fix the glitch&quot;.<p>2. Not that smart and definitely not a lawyer.