Lua is MIT licensed. The point is that if you have a GPL game engine and use lua scripts to turn it into a full game then you also need to license the scripts as gpl if you want to distribute the game.

(As others pointed out , oif you are looking for a loophole, game assets might be a better way to go)

But the Lua scripts would be bound to the underlying game engine. I would all come down to whether or not a judge would see it as a derivative work.