This seems to be the case: the wording is pretty obscure and IANAL, but the risk if you use React and sue Facebook for patent infringement should only be that t

This seems to be the case: the wording is pretty obscure and IANAL, but the risk if you use React and sue Facebook for patent infringement should only be that they can counter-sue you for any patents they may hold that apply to React. And be careful: if Facebook has any patents related to React, they could very well cover also the React alternatives: I seriously doubt that eg the author of Vue.js researched if they were violating and FB React-related patents. Edit: here the link to the patent grant https://github.com/facebook/react/blob/master/PATENTS https://github.com/facebook/react/blob/master/PATENTS > A "Necessary Claim" is a claim of a patent owned by Facebook that is necessarily infringed by the Software standing alone. This should mean that the patent grant only covers you from being sued for any patents covering React technology, and that is the only protection you lose if you sue Facebook.