I’m not sure how you’re imagining the game design should be specified, so possibly this will not be helpful. But for what it’s worth, my Inform game Bronze ( inform7.com/learn/eg/bronze/index.html ) has a license that permits derivative works. The site I just linked includes source code, but also a full map of the game’s rooms, a making-of discussion with a puzzle chart, and a walkthrough to the various possible endings. It is generally considered a full-sized but not monstrously large game, and demonstrates a range of classic IF functionality.