First, I think the Live Search is one of the neatest WP things I've seen in a couple years. I love playing with it, and it was the first tool I'd seen that I had a reason to install the REST API plugin for.

Second, I noticed they've put a second version of the REST API plugin (and listed it as beta) that's only compatible with WP 4.3beta and higher.... but I haven't yet found any explanation on why the split.

So the original plugin is only "verified" through WP 4.1.6, and the new one only operates on WP 4.3 and higher... leaving every WP 4.2 in an "unofficial" state? Yes, I know the original still works on WP 4.2, but this kinda goes towards the gaps in documentation issues all across the WP spectrum.