Maybe it's useful to React developers who have never seen game engine concepts. Most web developers have zero idea of how games are developed, after all, and teaching them a little bit about how to develop a game is going to expand their minds. Sure, that's a good thing.
But I haven't even scratched the surface of how many things are missing from React Game Kit, any of of which would be a showstopper. As another comment mentions, Pixi.js [1] is incredibly more useful in all ways.
It's a cute "Look at the bears dance!" demo, and criticizing the bears for not dancing well is possibly beside the point. But I also feel it needed to be said that no, one should not pick this up and try to use it as a game development platform. This is Hacker News, a site with lots of web developers who have never made a game or seen a game engine, and they may mistake the dancing bears for a ballet if they've never seen the latter.
On Firefox when using the arrow keys to read through the next, a single click renders two screens of text too quickly for me to read the first of them.
In any case, these explorations are important. They are small experiments showing us new ideas.
Look at this: http://reactnext.surge.sh/
That _is_ React. mind blown
I won't be making a game with it anytime soon. But maybe I'll borrow concepts and ideas from it, and make something else.
So don't worry. Don't let it puzzle you. Just sit back, relax, and stay tuned for what's next.