Elements is a bridge while the main project is rewritten. (It's in the name..."elements" of the original project.)

They stated in several places that it can't be "temporarily" fixed due to major structural changes to (I believe) the keyboard driver in Sierra.

Also pretty sure that Karabiner has been free forever. (Donations accepted, but you know how rarely that happens.)

Just keeping the record straight, as someone who loves the app and, yes was temporarily inconvenienced, but bravo to them for rapidly putting out something to tide users over.