By lacking faith in a God or gods I am not putting my faith in the position that a God does not exist.  Whether or not I accept the position that "God or gods does/do not exist" is a secondary questions.  

I've heard it expressed this way by others and it might make it clearer for you.  If you have a jar of gumballs of an unknown number and state that there are an even number of gumballs in the jar I can say "I do not accept your claim."  Doing so does not mean that I'm accepting that their is an odd number of gumballs in the jar as that is a separate question.  For that you need to move down a level to gnostic-atheism/hard atheism or anti-theism.

As for atheism being a religion, you and RolandX appear to be the wriggly ones.  Atheism is a position taken on a singular claim - The rejection of the claim "A God or gods exist." (Not necessarily the acceptance of the claim No God or gods exist).  Nothing else extends from that.  A position on a singular issue does not a religion make.