Their model is quite unlike FRP. Although Eve is evolving, it would be illustrative to study one of their influences: http://www.bloom-lang.net

This isn't FRP (incidentally, FRP has something in common with the relational and constraint systems of the past, but doing them functionally rather than via constraint solving or relation processing). And anyways, Elm is hardly the first language to support live editing and time travelling debugging (we've had that since the 90s in small languages), Elm doesn't even do this incrementally (it just replays the program from the beginning on each edit...not scalable).