In the flurry of IANALs in the comments, the readings of others seemed to match what bothered me:
nkohari put it best:
That said, if your use of React somehow violates one of Facebook's patents, you're in trouble. The original version of React would be protected by the additional patent grant, but your fork wouldn't be.
As nkohari goes on to state (which I agree with), they're probably just trying to protect their patent portfolio and participate in OSS.
I, however, don't want to both even being anywhere close to an idea of compromising F/OSS, as there are lots and lots of options out there that are well within and have no additional legalese that could be misconstrued (whether positively or negatively).
nkohari put it best: That said, if your use of React somehow violates one of Facebook's patents, you're in trouble. The original version of React would be protected by the additional patent grant, but your fork wouldn't be.
As nkohari goes on to state (which I agree with), they're probably just trying to protect their patent portfolio and participate in OSS.
I, however, don't want to both even being anywhere close to an idea of compromising F/OSS, as there are lots and lots of options out there that are well within and have no additional legalese that could be misconstrued (whether positively or negatively).