Business settings and ecosystems have in the past three decades been transformed by software utilization. It is being applied in several industries shaping innovation—platforms—and business characteristics, thus attracting ever more interest from both practitioners and researchers. During the last 10 years, research on software ecosystems (SECOs) has expanded, and is strongly related to the development of digital ecosystems. This expansion has led to the need to review the status of SECO research, and the present article provides a state-of-the-art literature review on the topic. We explain the connection between the relatively new research field of SECOs and the traditional streams of ecosystem research. This article contributes novel definitions of SECOs and SECO configuration, and proposes a theoretical model illustrating the relationship between vital contingency categories and processes. We identify significant research gaps and present a future research agenda.