Novak is certainly protecting someone we haven't heard of. He claims the guy isn't political, and I belive Novak on that score.
We don't know if he's told the grand jury. We do know he has not been held in contempt like some others but he won't say if he's appeared or not. I don't think we can conclude he's protecting anyone. He may well have testified who his sources were (there were two--non WH).