We aren't going to make any legitimate purchaser pay twice, John.
If you paid once, we'll ensure you get the full game.
Won't be easy, will it, though? Itch only allows an AVN if it's free, but you can't offer "free updates" so on Itch it would be free, but paid for on Steam. So I don't envy you get the rest of the game JUST to Itch purchasers of the game! (I hope at least you KNOW who the purchasers are!) :) I have faith in you, though. I think most purchasers, like me, would buy the game again on Steam, just to give you the income you deserve, so feel free to tell us all, if it's too hard to work out a way to get updates/the full game to us Itch purchasers, we will help YOU out, because of how GOOD this AVN is!