There’s actually a number of projects that started this way though I don’t know of any that grew up to be as charming and interesting as Serenity OS. Katawa Shoujo is one, though I could definitely see people complaining about the games content. The Tox encrypted messenger is one but I’m not sure that ever went anywhere.

I think most of them, like Andreas, dropped the association with 4chan pretty soon after the project started to gain real traction.