Calling atheism a religion is like calling bald a hair color, or not collecting stamps a hobby. Atheism is simply a lack of belief in a god or gods, nothing more.
It is, therefore, not a positive belief or a claim to knowledge. Instead, it is the default position of doubt, uncertainty and skepticism one may have regarding claims made by theists. Just as it takes no faith to lack belief or remain uncertain concerning any other imaginable claim, it takes none to doubt the existence of a god or gods.
Every human-being ever born begins life as an implicit atheist and must be taught the concept of theism or, more commonly, indoctrinated with it.
Atheism has no sacred texts, objects, places or times, no rituals or creation stories, no positive beliefs, central tenants, modes of worship or supernatural claims, no implicit or derived moral codes, philosophies or world views and no central organization or church. It fulfills none of the criteria that define a religion.
Common among many atheists is an appreciation for secularism, rationalism, humanism, skepticism, naturalism, materialism and freethinking none of which are implicit or derived from atheism, nor necessary in order to lack belief.
To say that atheism requires faith is as dim-witted as saying that disbelief in pixies or leprechauns takes faith. Even if Einstein himself told me there was an elf on my shoulder, I would still ask for proof and I wouldnt be wrong to ask. Geoff Mather