Okay, it's MIT licensed, and there's a patent promise - which i personally don't trust, but you're welcome to.
However, what the hell is a "CoreCLR" and how does it help?
I gave up on .NET back in the 2000s when I scoured MSDN for half a day to find out an overview for someone who wants to learn this "dot net" technology. Couldn't find any. I still don't know what they mean by .NET, and I have a feeling the meaning has changed every 2 years.
This is just the bytecode execution runtime, right? As in: no GUI libraries, for one - which makes it useless for porting Windows applications to other operating systems since, well, there aren't many command line Windows applications.
Actually don't bother answering. Honestly, it's been a long while since I cared what Microsoft does. You can make a very decent living as a developer while totally ignoring them.