This paper introduces the scientometric method of main path analysis and its application in an exemplary study of the paths of knowledge development and the roles of contributors in Wikiversity. Data from two scientific domains in this online learning community has been used. We see this as a step forward in adapting and adopting network analysis techniques for analyzing collaboration processes in knowledge building communities. The analysis steps are presented in detail including the description of a tool environment ("workbench") designed for flexible use by non-computer experts. By identifying directed acyclic graphs, the meaningful interconnections between developing learning resources are analyzed by considering their temporal sequence. A schema for the visualization of the results is introduced. The potential of the method is elaborated for the evaluation of the overall learning process in different domains as well as for the individual contributions of the participants. Different outstanding roles of contributors in Wikiversity are presented and discussed.