Microsoft, Netflix, and Twitter most likely have agreements in place with Facebook regarding the use license.

Source: I worked for a large company that had banned the use of React for all external facing projects, recently Facebook and their lawyers came to an agreement and now it's widely used.

Doesn't Netflix as well?

Yep, and Palantir also. I wish my company would be more open to using it, but the patent issue makes it a non-starter for us.

If you're MS, there are no ramifications.