React isn't as popular in the real world as it is on HN.
Hopefully they've all done their due diligence..
A lot of these groups still see front-end tech as just HTML and CSS..
If you don't have any patents, you're not really risking anything using React.
Bank of America was ranked 124th for its number of U.S. patents granted in 2016.
http://www.ipo.org/wp-content/uploads/2017/05/2016_Top-300-P...
https://github.com/facebook/react/wiki/sites-using-react
...that's obviously not complete, either. If you think of a large tech company the odds are they are using react somewhere for something, be it public facing or internal tooling. Many of the companies that aren't actively using React do so because they have their own JS stacks to dogfood (like Google and Angular).
If y'all think you're going to find some edge case that these companies lawyers haven't already...