Does the paid version have support for Retina displays? I tried the demo on itch.io and it doesn't seem to work w/ my Macbook Retina display, unless I'm missing some flags I should pass in or something?

No it doesn't do anything to work with retina displays right now. It's on my todo list but not too close to the top at the moment.

That does help a lot! I'll bump it to the top of the list.