I am implementing an online version of a card game. The author and publisher of the game owns the IP, evidently (e.g on mechanics and design).
the game (mechanics) and the graphics are our intellectual property - to be used only with our consent.
They are open to my publishing my implementation as open source - but in the interest of transparency, I'd like to pick the most appropriate license to a) ensure my work just doesn't get appropriated and used for commercial gain, b) ensure my work is not providing ways for someone else to appropriate their IP, if that makes sense (basically I don't want to accidentally screw them over) -- they are a small publisher, and struggling with pirate copies of the physical game.
Any idea or precedent of a similar scenario elsewhere? I could obviously just not open source this, but I don't see good reasons to do so, except my lack of understanding of copyright laws :)