What do you have to be?

[Metonymie]

Ladies and bruces,

I have a question about atheism.
As we know, being an atheist doesn't imply anything. It just means that someone doesn't believe in god (any god).

But is this true? Can you be an atheist and anything you like (except a believer in god, of course).
It seems to me, that you have to be a materialist and therefore can't be an idealist. (maybe in constructivist epistemology, but I'd doubt that)
(True/Untrue?)

If this is true, how do you deal with Hume's "is-ought problem" and naturalistic fallacies?

(David Hume
could out-consume
Schopenhauer and Hegel)