Collaboration in open-source projects: myth or reality?

One of the fundamental principles of open-source projects is that they foster collaboration among developers, disregarding their geographical location or personal background. When it comes to software repositories collaboration is a rather ephemeral phenomenon which lacks a clear definition, and it must therefore be mined and modeled. This throws up the question whether what is mined actually maps to reality. In this paper we investigate collaboration by modeling it using a number of diverse approaches that we then compare to a ground truth obtained by surveying a substantial set of developers of the Pharo open-source community. Our findings indicate that the notion of collaboration must be revisited, as it is undermined by a number of factors that are often tackled in imprecise ways or not taken into account at all.