Yes, but it costs a lot of money to buy (Ren'Py is free actually.) It's available on Steam. I don't know if you're familiar with the RPG Maker series, but it comes from the publishers of those games. Maker series are known to sell asset packs as DLC. So things like characters, backgrounds, and music. If you made some pack with a bunch of characters maybe you could sell it as a DLC as well as sell it individually, you would need to work out those details with the devs. Just a thought.