I just registered here - the C&C folks will recognize me, but many of you won't...anyway, I felt the impulse to chime in, as a C&C playtester.
C&C is *so* different from AD&D that I could easily spend the better part of an hour posting on its differences. It is *not* intended to be an end-run around copyright to emulate 1E, because if this were the case, it has already failed miserably at that intention. I can't emphasize enough how horribly inaccurate that supposition is.
If 1E materials should be "compatible" with C&C, and vice-versa, this is purely because C&C builds on tradition *and* modularity, and opens itself up to simple conversion from a lot of sources.
There are a lot of "nods" to the old school that manage to capture the proper feel while reinventing and improving the mechanics involved. The most it could be called is an "homage" to the old school. In reality, all it does is recognize that "old school" is just as valid a form of play as any other.
There are a lot of new concepts, and dare I say it, *better* methods of doing things, I feel, than in any other version of the game, OGL or not.
C&C isn't meant to be a D20-"lite" any more than it is meant to be a "AD&D-now". It's meant to be C&C, and it is its own approach to the game.
So, if anyone is looking for a brief description of what the game is about, it's this:
The idea is to put the game back into the hands of those who play it, and not in the hands of a bunch of detached game designers. The framework will be simple and easy to change, and the implied permission will be in place to change it to reflect any preferred playing style, whether by using other OGL features, or adding custom features. The game will be playable as-is, but it also recognizes that gamers like to tinker and mold, and rather than confine that creativity to a small, publisher-defined set of "interfaces", C&C kicks the door open and says "Do what you want - I'll get out of your way."
I hope this helps clear up misconceptions.