Seems to me the more problematic part is clause b: The license granted hereunder will terminate, automatically and without notice, for anyone that makes any cl

Seems to me the more problematic part is clause b: The license granted hereunder will terminate, automatically and without notice, for anyone that makes any claim (including by filing any lawsuit, assertion or other action) alleging ... (b) that any right in any patent claim of Facebook is invalid or unenforceable. Doesn't that mean that if Facebook sues you for patent infringement in something else you did (possibly unrelated to React) and you disagree, they can take away your licence to use React? In other words, Facebook could arbitrarily shut down your use of React by filing a spurious patent lawsuit against you. And if your use of React was critical to your business and Facebook didn't like the look of your business, that could be dangerous.