What I want to do is the reverse. Instead of giving Steam Keys for who purchased my game here, I want to give keys for who purchased on Steam to have the game here as well. Is it possible somehow?
Ok, but how I know who purchased the game or not? Is there any way to make this automatically?
Yes, you can mark the keys as having to be claimed before people can download the game. That counts as a purchase, and makes it so nobody else can use the same key anymore.
No, I mean, how I know that the person purchased the game on Steam, so I can distribute the keys automatically for them. Something like with that .CSV file system of Kickstarter.
Err... you have to figure that out on the Steam side?
Ouch! They don't have any system to let us know who purchased the game, as far I know… -_-'
I don't know anything about selling on steam but I bet you could put a menu option in your game that ties in with the Steam API and requests an itch key from your own server.
That's a good idea, but I removed my games from Steam, I don't know if their API still works for them.
Also, I have a RPG Maker 2003 game that doesn't have support to the Steam API anyway. =/