Skjor is back from the dead. Hes just walking around Jorrvaskr chilling as if nothing ever happened.

Its not a bad thing though. He still gives me missions even though I am harbinger.

Yeah, this isn't supposed to happen. It's a bug that has been around since the game was released. Skjor gives the same types of quests as Vilkas, so there really is nothing to be gained from having him alive again. I'd be careful about accepting quests from Skjor though, because they may possibly end up getting bugged, because he's bugged when (or if) he comes back from the dead.