I am confused. I thought I would try and use a new game engine in order to expand my abilities, and found a nice engine called springrts. I was looking through the licensing info and it is licensed under the GPL 2 licence. If I remember correctly, does that mean that anything I make with it, I have to distribute the source code to?
Under the proprietary section they say this:
From Spring Engine - Games.
So it's not the code that makes them different, and they are following the GPL.
No, in this case it does not.
In their list of games they are pretty clear that they consider the game data as using the engine rather than being derived work of it. So GPL does not apply to the game data.
Therefore you can put the game data under any license you want including fully commercial. You still have to provide download of the engine sources somewhere, including possible modifications you make to the engine code itself, but you don't have to do it for the game data source.