A Limited release. Perhaps some sort of self-made installer that records the time stamp as your installing the game. It will only allow the game to run for a certain amount of time and then poop out after the time period is up.
There are many ways to distribute a full version engine with only a level or two and make sure it doesn't go anywhere other then the computer it was intended for.
There are many ways to distribute a full version engine with only a level or two and make sure it doesn't go anywhere other then the computer it was intended for.