By the letter of the law -- which should be the basis of referees' judgment -- he committed no penalty. However, I do not believe he was pointing to the back of the net for Richards to send it there. He looked back at Kipper before each indication with the stick, and both impeded Kipper's vision. He then took his eyes off the puck on more time to throw his hand up, palm toward Kipper, right in front of Kipper's face, which drew the slash from Kipper, and then the shot came in.
Since he wasn't facing the goaltender, it wasn't a penalty, and it shouldn't have been called. The Flyers should be the victors. However, I do believe the league should look at this and change the phrasing of the rule so that players cannot hand-wave at all in front of the net. It would make setting screens way too easy. Just follow the goalie's mask with your hand.
I reiterate, however, that the Flyers got screwed on this call based on the rules as they are currently written. But I think Pronger knew exactly what he was doing.