Portions of .NET are under ECMA and ISO standards: 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/
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.
Shh, they might find us.
The crux of the Oracle v Google suit is basically, "It's Java, but it's not Java Java."
If you take a look at the MS patent promise, the way it's authored specifically allows for the very same kind of suit.
Say what you will about the Android Java situation, but it doesn't exactly scream "this is open and free software."