1. There are more than one kind of Buddhism. I believe the applicable kind for this question is Zen, not Theravada. (Theravada falls squarely into what most people consider “religion,” Zen skirts the boundary between religion and philosophy.)
2. There is no objective answer to this question because there is no objective and perfect definition of “religion.” Some people define religion broadly, to mean any broad philosophy or ideology. For my part, I prefer to define religion more narrowly, as an ideology centered around the worship of a deity or deities (who are, in turn, defined as powerful beings with personalities who are interested in human history and morality). So I would not call Zen a religion, but I would not care if someone did.