But what if you have a legitimate patent claim against Facebook that doesn't relate to usage of react? It sounds like if you pursue that, then as a result, you can no longer use react. Or perhaps I'm missing something?
That seems entirely reasonable to me. If you want a free license to Facebook's patents, you have to implicitly give them a free license to yours as well. If you want to get money from them for patent violations, you should be prepared to then have to pay to use their patents.
Facebook only grants you patent license related to React, but you have to pay with every patent license your company have.
It's like saying Facebook can use all Google's patent, from search engines, Androids, Google car, etc. All because Google use React in a single presentation page.
It's even more viral than GPL. At least with GPL, your code only becomes infected with GPL in derived works.
But Facebook has all access to even your unrelated patents.
But what about if you're a large company with a large patent portfolio, you don't intend to abuse silly software patents, but it would be irresponsible to de facto grant Facebook free license to all your patents?
If I'm doing a startup, this clause is no issue. If I actually have patent assets, this seems like a non-starter still.
I was among the people who warned about the unfairness of the previous license. I am a Free Software advocate, so I have no problem with allowing Facebook to use any patents I might later obtain, as long as using React (and similarly-licensed software) does not leave me defenseless against a FB lawsuit.