itch.io

Yes, you can use it just dont charage for it money I geuss. Its just give the artist credit. (yes this is not a good answer) I forgot the name but there is something about work of art that it belongs to the artist. As a designer its probably cool to see your design in action. Still not a good structed answer but here you go.

Have you tried contacting the designer directly? I contacted the designer of the cartridge I want to do and he was glad to hear about this game jam, happy for me to make the game, and super helpful too.