Update 2012-01-28: Springer changed the citation. The reference below reflects this.
Springer just republished our 2009 article on how vendor-owned open source works, again. Here is the abstract:
Abstract: Single-vendor commercial open source software projects are open source software projects that are owned by a single ﬁrm that derives a direct and signiﬁcant revenue stream from the software. Single-vendor commercial open source at ﬁrst glance represents an economic paradox: How can a ﬁrm earn money if it is making its product available for free as open source? This paper presents the core properties of single-vendor open source business models and discusses how they work. Using a single-vendor open source approach, ﬁrms can get to market faster with a superior product at lower cost than possible for traditional competitors. The paper shows how these beneﬁts accrue from an engaged and self-supporting user community. Lacking any prior comprehensive reference, this paper is based on an analysis of public statements by practitioners of single-vendor open source. It forges the various anecdotes into a coherent description of revenue generation strategies and relevant business functions.
Reference: Dirk Riehle. “The Single-Vendor Commercial Open Source Business Model.” Information Systems and e-Business Management vol. 10, no. 1. Springer Verlag, 2012. Page 5-17.
You can read it online, download a PDF, or use the Springer site.