They stated on their forums that they're allowed to sell the back issues as long as they last.
Oh, about the comic, they also said that Dragon and Dungeon were profitable. It wasn't Paizo's decision to end the license. (Though I understand that all involved are still friends, Wotc apparently bent over backwards to give Paizo the time to transition to Pathfinder.)
And if someone for some obscure reason wants my opinion on electronic 'piracy', I think that Eric Flint says it better over at
http://www.baen.com/library/
/Jonas, looking forward to his shiny new toys^H^H^H^HPathfinder issues.