You already paid the creator for knowledge of how the effect is done and performance ability. The DVD is just the means through which that knowledge if transferred. It's that the creator was given what they deserved, and that you put the knowledge to good use.
So no, reselling the DVD really shouldn't be a moral issue. Unless you take into account that someone is benefiting from knowledge that they didn't purchase from the creator. But that gets in to a whole different issue.
-ThrallMind