If you define it as the study of who we really are and our relationship to the cosmos, then one can have a religion that includes a diety or one that does not.
I define religion as the worship of a Higher Deity. Even the root of the word “religion” refers to this -
religio ( religare), meaning a bond between man and the gods.
Meanings change, and we have seen groups change the meaning of words even in the last few decades. “Gay” used to mean “happy”. “Hero” used to denote someone who put their life in danger to aid another. “Religion” also seems to be going through a change to become an all encompassing word with little meaning left.
Buddhism is 26 centuries old. Is it a religion?
I don't think it is too big a stretch that if you say "there is no such thing as God," or if you say, "nothing transcends material reality," you are making a religious statement.
thanks for your reply.