Previously literature on the role of firms in open source software (OSS) development is mainly based on qualitative data and case studies rather than on proper data sets. Research has shown that firms involved in OSS development generally face the challenge to balance the tension between the wish for external knowledge and the demand for control. As it is not entirely clear how firms deal with this tension the goal of the paper is to deepen the understanding of the use of external knowledge, especially in firm-driven OSS consortia. Based on a theoretical background a research design and resulting hypotheses were developed. The data set is based on an agglomeration of a specific firm-driven community and consists of 912 committers and 116 firms organized in 109 independent projects.