Collaborative research projects dedicated to information and communication technology and supported by the Framework Programs of the European Commission result often in both partnerships among involved companies and prototypes of common, composite software products. One problem of commercializing these common products is the transition from a project to a commercial setting and the development of a suitable inter-company business model. In many cases none of the involved companies is able to take over the responsibility for the common product based on approaches involving joined ventures, binding supplier contracts or buying of licenses from other partners. Thus, flexible business models are required that are based on loose partnerships among involved companies, but still enable a common presence on the market. By drawing from and combining aspects from the concepts of value networks and software ecosystems, this paper provides two results: a design procedure and an overview of design options for development of inter-organizational business models for composite software products based on loose partnerships among involved companies.