tranquil

The license is ISC, so you can do whatever you want with it. in order to call back into lua you can either use the standard C api. (This file from another project of mine might be a useful starting point: https://github.com/aptiva/Tranquil/blob/master/Tranquil/Core...) Or use addMethod to add a lua function as a method to a class (You can use createClass to create a new class) I'll add a subclassing demo to the readme later today

Take a look at the app that the OP is building. It's pretty interesting and uses this scripting bridge for generating OpenGL visuals. (http://github.com/aptiva/tranquil)

It was designed for use for scripting within an objc app. (http://github.com/aptiva/tranquil to be precise) It doesn't support subclassing objective-c objects so that would probably limit you if you tried to write your app exclusively in lua.