I think Snape was never a trader, because he was never on the Orders side. I think he was only being good around Dumbledore to stay out of Azkaban just like he said. I truly believe Dumbledore is gone and Snape is finally out there as a Death Eater. I mean, even if Dumbledore isnt dead, everybody thinks he is and that Snape killed him so what good does that do?