> The license granted hereunder will terminate, automatically and without notice, if you (or any of your subsidiaries, corporate affiliates or agents) initiate directly or indirectly, or take a direct financial interest in, any Patent Assertion: ... (ii) against any party if such Patent Assertion arises in whole or in part from any software, technology, product or service of Facebook or any of its subsidiaries or corporate affiliates,
I always thought the main problem was this part, where you basically lose the license or your IP if Facebook ever decides to become your competitor, e.g. you start a company with a react front-end that does X, and then Facebook decides to directly copy your business. You have no recourse against Facebook, because if you sue them for infringing your IP, you lose the ability to use the React license.