Peer production
As the open source development happens by open sharing of the main means of producing (as long as you can afford the material conditions of using the means, that is: have a computer and preferably an Internet connection), it doesn't happen through a mediation by money, but through direct exchanging or bartering. As it also is a form of social, communal production, people don't merely labor on their own code, but collaborate for a universal code. Thus, a technical consequence of the adopted practice is, that an open source development doesn't work in hierarchic manner, nor does it have any fixed organization. An open source community constantly organizes itself through peer-to-peer relations of collaboration on mutual project that also divides to multiple side projects (every participants personal use of the code).