Snowden certainly started out as a whistleblower. And as the vast levels of NSA snooping were deliberate, reporting it internally would be pointless - management already knew.
I think he's revealed a lot of stuff on how NSA operate, and I remember a few leaks of unrelated stuff about SIS and GCHQ - none of which seemed to be anything other than spies spying on foreign governments. Which is entirely legitimate. So I'm not sure what you'd call him now. Do we even have a word for it? Revealing operational details of legitimate national security operations makes you a traitor, but that seems rather harsh, and his revelations didn't start out that way. It's all rather confusing really. I'm sure Smiley would be able to sort it all out.