The first thing I do now on each Facebook open-source reveal, is to check the PATENTS file for the toxic second paragraph, to see if they've changed it. Sadly, no. I can't imagine being able to use this at any decent-sized company with lawyers. :-( https://github.com/facebook/react-native/blob/master/PATENTS
See for example the discussions at https://news.ycombinator.com/item?id=9111849 (eg. https://news.ycombinator.com/item?id=9113515)
Full disclosure: I work at Google, where many are sad to not be able to use recent Facebook code.