One thing:
Khazad as of now is hardly a clone of anything. It's meant to be a game *inspired* by DF's Fortress Mode.
"Inspired" can mean a few things.
Take a look at this file. Anything look familiar to you? Almost all of it should, because it's not just "inspired" by DF, it appears to be a damn near exact re-implementation of it, with a few changes where Impaler feels he wants them. This isn't just "inspired by" DF, it's looking to be a clone in every sense of the word.
He's not just taking DF as inspiration, he's taking it as his sole inspiration (for the most part). He's trying to make DF, but better. This is clear from the above feature/goal list.
Here is the problem: Unless you actually steal something directly (he did, I know) you can remake just about anything you want so long as you don't use things that are able to have a copyright applied to.
Can I make a game where I run and jump as an Italian plumber, who eats mushrooms and stomps on turtles? YES.
Can I call him Mario, and make the mushrooms red and brown, and the turtles have wings and yellow faces? NO.
There are limits, and there are rules to copyright. You can be inspired by DF enough to make your own--from scratch--and short of calling it Dwarf Fortress, and using the same data files... there really isn't that much one can do. There are no 'graphics' to speak of, so Toady wouldn't be able to claim copyright on that... but what i see is that he wants it to be full 3D anyway, so that is kind of a moot point anyway.
even if you brought the full force of the DCMA down upon him, all anybody would have to do is wipe everything clean, and start building from scratch and never use any data from DF and he would be *technically* allowed to do so.
it is still however, a completely and utterly absurd idea to attempt to make a game as deep and as complex as DF by starting with what the walls and doors look like... kind of like picking up a screw and some metal and saying you are going to make a motorcycle that looks like a BMW.
I am not advocating theft, I am simply stating that anybody could pick up and make a text-based game that feels a lot like DF without it actually containing one bit of code from DF and it would be allowed under copyright. see the "Microsoft vs. Linux" fights if you want more examples of this.