Hey, I've been wondering the same thing, I hope the author is doing ok and is well. FYI - yes you can buy it here on itch and you can then download it for Mac AND for Windows. No copy protection methinks. You can also buy it on Steam, which helps when moving to other computers (although with itch.io that should not be a problem too, just I know Steam better).
I think the memory reqs are because there is a lot of overhead going on in positioning and calculating light and shadows on the fly.