The facebook patent clause states that you lose the licence rights to use react if you sue facebook against any patent infringement (for patents you own).
There is nothing in that saying that they have patents on react, and if they have patent covering, it very likely covers very much more than just react (because of the generic way patents are filed).
«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»
see https://github.com/facebook/react/blob/master/PATENTS
No, this is wrong. You do not (and cannot, since it’s BSD) have your license to use React revoked. You do have your additional patent grant revoked - that is, if you sue Facebook for patent infringement, you will lose the right that they previously granted to use any and all patents covering React.
If we assume that any patents covering React also cover the alternatives such as Preact, the nothing is gained by avoiding React.
You should read more carefully, or listen to interpretations from lawyers. The license referred to in that document is the license to any Facebook patents granted within, which might not even exist.
The patent grant is separate from the copyright license.
There is nothing in that saying that they have patents on react, and if they have patent covering, it very likely covers very much more than just react (because of the generic way patents are filed).
«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» see https://github.com/facebook/react/blob/master/PATENTS