Only if they have a patent on [edit: something in] React, or on anything else that you use (regardless of it's from Facebook) [edit2] Also, patent lawsuits ar

Only if they have a patent on [edit: something in] React, or on anything else that you use (regardless of it's from Facebook) [edit2] Also, patent lawsuits are costly. If you're going to start one against Facebook the cost of switching away from React first would be negligible.