Read the full patent grant. > The license granted hereunder will terminate [..] if you [..] initiate [..] any Patent Assertion: (i) against Facebook or any of

Read the full patent grant. > The license granted hereunder will terminate [..] if you [..] initiate [..] any Patent Assertion: (i) against Facebook or any of its subsidiaries or corporate affiliates > [..] Notwithstanding the foregoing, if Facebook [..] files a lawsuit alleging patent infringement against you in the first instance, and you respond by filing a patent infringement counterclaim in that lawsuit against that party that is unrelated to the Software, the license granted hereunder will not terminate under section (i) of this paragraph due to such counterclaim. https://github.com/facebook/react/blob/master/PATENTS https://github.com/facebook/react/blob/master/PATENTS In other words: if Facebook sues you (and it can't be about React if you use FB's React with the grant) and you countersue, the grant will ONLY terminate if the patents you use concern React. So you can still defend yourself as long as you don't attack React. EDIT: FWIW (ii) and (iii) are basically scenarios where you sue other people over using React, so those aren't really relevant when trying to countersue Facebook.