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.