Protecting Myself

So, I've been reading all these stories online about tiny developers who make the interesting a new games only to have their games stolen quickly by bigger developers.

Now, I don't nearly have a game yet, BUT, someday I might. Right now I have a few building blocks of the massive structure of a working game. If some day I decide to sell it (or, more likely, give it away along with a "Donate" button), I will probably need to find a way to protect my code somehow.

The real problem here isn't that I think someone is going to steal my work and make money off it. That's fine, I don't mind if people do that at all (yeay free-flow of information!). The problem is that they could sue me if they copyright code based on mine, unless I can prove that I did it first. 

Also, just because I'm a coder and full of myself, I'd also like credit where it's due. If some one uses some of my code to build their awesome million dolor game (lol, no, that would never happen!), then I want credit (well, really I'd like a cut if I can get it, but w/e).

Licences I'm looking at:
Apache License

Creative Commons (they have a few for different uses)

CopyLeft
GNU General Public License

Any others that I missed?
Thoughts? (comments below)