Usually credit is more than just a 'nice-guy' thing, think of it as plagiarism. (if you were in school, you'd get a big fat F!)
And if you are a good programmer, with C++ knowledge, then making your own rts shouldn't be too hard. if you get it done, do post it somewhere so others can see too! (I just happen to really love RTS and RPG games, and of them, Glest is the only one that's free and worth playing.)
And from a consumer point of view, if you make a game and plan on charging credit, you should offer a trial or demo first, just a tip!