There are a couple of ways to make money from OSS. My fav is having a paid managed version. Ghost[1] and Discourse[2] are good examples of this. (I am using the same model for a personal project [3]). See https://github.com/nayafia/lemonade-stand for more ways.

[1] http://ghost.org [2] http://discourse.org [3] http://suet.co