itch.io

I do not know for the steam key or what ever, but to update the game, click on the buy now (you do not have to buy it again) and at the bottom of that page you will see "I already paid for this..." and it can help you know how to access your paid games and update your version

dont think it will be out on steam because people who already bought the game will have to buy it again or the owner has to go one by one to send the people who bought it a steam key