From A Different World - Forums

You are not allowed to kill anyone with the charged axe on the map rooftops, it's considered RDM and it doesn't matter if you're traitor or not. It's not the same as prop killing, due to the fact that anyone that touches it dies instantly.

But doesn't that mean it's kind of like the knife in a sense?
I mean
If it's an instakill weapon like that
Shouldn't it be okay for traitors?

You still have some control over the knife since you gotta left-click/right-click with it to kill someone. If you're just holding the axe and walking with it, eventually you will accidently kill someone if they walk into it.