Yeah, but ID is the exception to the rule. I really doubt that the big
publishers like Activision, EA, Nintendo, Sony, and Ubisoft are ever going to
release their game source code. Even if they remove all of the art, they will
be scared about their code being on the net. There were big legal
implications when Half-Life 2 source code was leaked and recently with Mass
Effect 3 before the game was out.
Plus I think many of these games licence engines like Havok and Unreal Engine
which would then require the creators of those engines, who make their money
off of licencing, to release the source code. That would NEVER happen as
Activion or EA could simply take the source code for the Unreal Engine and
create their games by totally bypassing the original creators of the engine.
The Unreal Engine creators would no longer have a business model, fire
hundreds of employees, and basically go out of business.
Sure its nice to get the source code to make something. Just be prepared to
maintain it. We all saw what happened with the Objective-C source code when
they were forced to release it under the GPL. The GNU version is an unholy
mess while the Apple version is maintained and production ready.