Is there a way to just buy the game without being a subscriber?
Unfortunately not currently. Because it is still in development, we haven't figured out a price point for getting the game with ongoing updates. If we eventually sort that, or get to a v1.0 we'll have it for individual sale.
You are able though to sign up and just cancel same day - you'll still get access to everything for the month without the chance of getting rebilled at the end.