That sounds more like a main project rather than a side project. My side projects are just things that I want to experiment with or that are based upon ideas or technologies I just wanted to screw around with at some stage. They could become my main project one day but that's not really the goal otherwise it'd be my main project already..

Maybe you lose interest/motivation after a long time of not launching or it just doesn't go anywhere and it could be valuable to another person.