The game will be free so there's no need for keys and I do plan on having an optional subscription model for dev builds after early access releases. You will be able to vote on things and get the content faster than the free builds, all content is eventually free though, nothing is indefinitely gated. I think I will use subscribestar and not patreon however, since the latter is very picky with their NSFW guidelines.
KIckstarter backers will get access to these dev builds in the future as well yeah, basically anyone above the 15 bucks tier gets the full game forever.
Thank you for the support and kind words <3