They are atheists, pure and simple. Atheism is a religion just like any other belief set. Christian Atheism is an anachronism that cannot be reconciled, especially with their "statement of faith". They either believe in a God, or they don't, there is no grey area. If they believe "in" Christ, then they must acknowledge his claims, if they believe "about" Christ that is no different to believing "about" Hitler. i.e. He existed and probably did some of the things claimed of him.
I consider myself a "Pagan aetheist".
The stories, structures and ethos of modern paganism appeal to me immensley but I have no "faith" in them.
Its odd that not believing in any god should need a name at all. Its not a religion its just common sense.
The God within instead of without.