I reckon he is good. Heck, I don;t even think Dumbledore is dead, but hey, what do I know.
I don't think he's dead, because that's not the typical effect of an Avada Kedavra spell. Is says he floated into teh air and fell to the ground, but in the other books when the spell is used, a green light fires out of the wand, killing them instantly, so therefore, I don't believe he's dead, and if anyone tries to convince me otheriwse, I won't listen.

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Anyways. Snape I think is good to a certain extent, I don't think is a freaking angel or anything, I just don't think he is under Voldemort's command. EIther he's pretending, and working for himself or some other idea like that. Personally, I just don't think that he is as evil as is described. I reckon that in the seventh book there will be a huge twist to the story, making him be on Harry's side.
But hell, that's what I think.