Isn't the style of programming react imposes (unidirectional data flow and component composition) the real innovation for front end applications here?

Sure the dom diffing technology was hot at the time it came out but it's basically is a commodity item at this point.

In that sense, the open source community can (and should) build multiple react clones that are licensed more liberally.

Sure, I'm annoyed by the licensing of React too, I think abou it a lot. But does it really matter that Facebook won't budge on this? The technology is out there whether it's React or not.