How can a religion by atheistic? Isn't that an oxymoron?
Emile Durkheim suggested that religion could largely be characterised as a form of social organisation, in terms of providing a set of moral norms that inhibit anomie or moral lawlessness. In historical terms, religion has tended to function as the crux of social organisation, whether this refers to churches being the centre of village society or establishing schools in nineteenth century Britain. Nonetheless, the diminshing role of religion in increasingly secular and materialistic societies suggests that this social role is one religion is ceasing to be able to fill. As such, there seems little reason why atheists are not able to appropriate the social function of religion to form communities.
Memetically we can describe religion as generally involving a phaithlike adherence to a particular mythology. As a historical note of some mnemonic significance, religious mythology traditionally involves some sort of supernatural ontological violoation. But this exists largely as consequence of the exigencies of story-telling and human memory in an oral tradition. Religiouslike behavior in a more literate society can involve less supernatural mythology of no less overall significant emotional impact. For example, Ayn Rand's Objectivism movement built on the mythology of her fictional works "The Fountainhead" and "Atlas Shrugged". Also witness the cult-like group mentalities that can play through various sci-fi communities, like Trekkies. Atheism does not in any rational way preclude someone from participating in religious instutions, behavior, or even mythologies per se, only in embracing supernaturalisms in some literal non-metaphoric ways.