Since its origins, the diffusion of the OSS phenomenon and the information about it has been entrusted to the Internet and its virtual communities of developers. This public mass of data has attracted the interest of researchers and practitioners aiming at formalizing it into a body of knowledge. To this aim, in 2005, a new series of conferences on OSS started to collect and convey OSS knowledge to the research and industrial community. Our work mines articles of the OSS conference series to understand the process of knowledge grounding and the community surrounding it. As such, we propose a semi-automated approach for a systematic mapping study on these articles. We automatically build a map of cross-citations among all the papers of the conferences and then we manually inspect the resulting clusters to identify knowledge building blocks and their mutual relationships. We found that industry-related, quality assurance, and empirical studies often originate or maintain new streams of research.