They could though! Microsoft has a long history of “embrace, extend, extinguish”!
You may be willing to put your company at risk because you trust Microsoft but I’m not going to.
Feel free to do you, I have told you this already. Seeing you’re unable to drop the conversation, when did Microsoft ever sue someone for using C#? I trust Microsoft far more than Oracle (reasons detailed in another comment). However, I do not run Microsoft software at my company at this time, other things work better for what I need.