I believe ADK's claim. Just read John Pope's wiki entry, and the only alignments that make sense for him are town or 3rd party. Since ADK already gave up his provided fake claim I think he's almost certainly telling the truth.
(more details: looking at John Pope's wiki entry, there's no way he has a flavor number higher than 5. Ash's setup post strongly implies, though I guess it doesn't say outright, that provided fake claims would be higher than 5, so I don't think it's possible that Matt Mason and John Pope are both fake claims provided to different scum players. ADK is either telling the truth or he took a shot in the dark that John Pope isn't in the game, which seems like an insanely high risk move as scum.)
Given that, I think we should keep him alive, because he's more like town than he is like scum, at least as long as town is winning. I don't love keeping him alive with a dayvig shot that he could use on us if the tables started to turn.