It is true that you get pre-release builds if you're a patron, but as far as I know, the game remains free and you will be able to download 0.8.0 for free once it comes out.
Obviously, please don't think that 0.8.0 is in the playable state right now. What you get is pretty much development master branch builds, they're here just to show appreciation for your support by giving you a peek at the future content and a place to mess around in as you wait for the proper release.