I'm known to hack on 2D tilemap rpg engines, here are some experiments. The only one I can recommend looking is the first. The clojure-repo contains some interesting ideas, but it's impossible to develop it further. The qt-repo contains interesting (as in "I can't believe that elephant dances") ideas too, but it's... quite complex, so I'm not developing it further
The Common Lisp repo is written against SDL, and if I had assets and a script of a game, it should be as production ready for making a game as it can be.
(even though I have to admit I'd probably use SpriteKit instead of custom homegrown engines)
Keywords: Common Lisp, Emacs Lisp, Clojure, C++, Qt, ECL