Cookie Clicker is a JavaScript idle game by Orteil.
For a short time, I was working on a port of Cookie Clicker to NES. But I canceled it when early signs of game-induced RSI began to affect my ability to function otherwise.
Technical features:
"Feel free to port it, as long as it's non-profit"
Licensing issue: Thus Cookie Clicker is non-free by Debian's definition, and I will have to take care to separate Orteil's non-free contributions (pictures, names, flavor texts, price tables) in the source code from generic idle game logic to keep the engine free.