24 March 2013: If you're reading this note, then you've encountered this section while it's undergoing substantial revision; see producingoss.com/v2.html for details.
Mention Software Freedom Conservancy, SPI, ASF, GNOME, any others. Note "non-profit" vs "not-for-profit". Mention Kuali et al as models. Problems of consortiums. Don't assume the U.S. tax code benefit is familiar everywhere. Emphasize clear separation between the legal infrastructure and the day-to-day running of the project: the organization is there to take care of the things the developers don't want to deal with, not to interfere with the things the developers already know how to do. Explain fiscal sponsorship when talking about fundraising. Note trademark ownership as well as copyright ownership, and link to this section as appropriate from the licensing/copyrights chapter and from the money / corporate involvement chapter.