Ah, the old "You're not our friend so its not our problem". While I do not have any ideas on how to deal with it outside of emailing them, the least I would do is make a disclaimer in your app's listing stating clearly that you are in no way affiliated with this "Pro" version if you haven't already. Better to save a few of those potential customers then lose them to the person who ripped you off. As far as getting the listing removed.. I'll leave that up to the powerful HN mind.