Open source software projects rely on groups of volunteer contributors who collaborate to produce code and documentation. Their work is often coordinated and supported by online communities, which are essential to sustain open source projects. In this paper we analyze the structure of the underlying social networks of online communities of practice. We analyze the emergent structure of five online communities associated with highly successful open source projects in order to identify the structural correlates of successful projects, as well as moments of vulnerability in community structure that could be monitored and proactively addressed. Specifically, we consider the structure of the core of five established online open source communities. Our findings demonstrate that the core of the largest strongly connected component these communities is the most sustainable part, and the rest of the largest strongly connected component is more vulnerable to the loss of contributors and collaborators. Moreover, we analyze the evolution of the community structure over time and demonstrate that the period just prior to the emergence of the largest 2 edge connected component inside the core of the communities is the most vulnerable point in the life cycle of online open source communities.
PACS: 0000, 1111
2000 MSC: 0000, 1111