It wouldn't require a complete change, they are (from what I've heard) doing a Java API, and because of that they'd only have to expose the functions of the Java API to a Lua VM (maybe with a few minor changes). Lua is, in my opinion, a
much better choice than Java, just for the reason that you'd have to compile Java every time you want to change behaviour of your Program. Lua also integrates better with C/C++ and is more flexible and less heavy-weight than Java, because Lua doesn't need a complete runtime environment installed (as opposed to Java). Upvoted.