> I mean, if you can use the software without the patent license, what is the patent license giving you?
Facebook may or may not have some patents covering concepts or algorithms used in React. If they do (nobody is aware of any), then they could sue you for using React, or any other framework which uses the same underlying concepts (eg, Preact, maybe Vue, possibly Angular 2.x, etc., depending on what the patents cover). If they did sue you, a valid patent grant (which you obtain by using React) would be a very strong defence, and would be quite useful.
I'm not entirely sure what you're trying to say. The patent grant applies to Facebook's patents (if any) on the tech used in React.
> I think the patent grant applies to everything you make
Yes, if you have a patent grant from using React, it would be a defence from claims that things you have written that do not use React violate patents included in the grant.
I just re-read it, you're correct. It only covers React
> For avoidance of doubt, no license is granted under
Facebook's rights in any patent claims that are infringed by (i) modifications
to the Software made by you or any third party or (ii) the Software in
combination with any software or other technology.
Facebook may or may not have some patents covering concepts or algorithms used in React. If they do (nobody is aware of any), then they could sue you for using React, or any other framework which uses the same underlying concepts (eg, Preact, maybe Vue, possibly Angular 2.x, etc., depending on what the patents cover). If they did sue you, a valid patent grant (which you obtain by using React) would be a very strong defence, and would be quite useful.
The value is real...but quite narrow in scope. :)