its like paying a subscription i guess, in order to play the game you have to pay 8$ and if you want to receive new updates you have to pay 8$ monthly because the dev updates the game monthly. the itch.io version is the alternative way to play the game if the players are having a problem subscribing him on subscribestar. tho i do still wonder when will the full game release so that we can just buy the game once and receive small updates for free lol.