I've been reading up a bit about alternate ways on how you'd be able to add real mods to this game instead of just forking the sourcecode.
I came across this interesting article.
http://www.moddb.com/games/overgrowth/news/choosing-a-scripting-language
It was written in 2010 by one of the developers for Overgrowth, a game written in C++.
He talks about what scripting language to use for their game for the following reasons:
First, it makes gameplay programmers more efficient by reducing the amount of time they spend waiting for their code to compile. Second, it helps enforce the division between the game engine and the game itself, encouraging modular and reusable code. Finally, it allows players to write their own scripts, resulting in much more complex and interesting mods.
He then goes on to compare Lua, Javascript and Angelscript.
He eventually picks Angelscript as his favorite because of its syntax being very similar to C++.
It has native support for C++ functions and types, so it is very easy to hook up to the game engine. The syntax and structure of the language is very similar to C++, except with garbage collection and a few simplifications. It also supports operator overloading, and even comes with example code for setting up a 3D vector type.
Something worth considering?