Adoption of open source software (OSS) principles to internal software development has gained considerable momentum. Often labeled as "internal open source" (IOS), several large firms have started to implement these programs. Research to date has mostly focused on facilitating IOS adoption. In the present research, we focus on how IOS affects reuse. Employing a qualitative case study, we examine the IOS program at IBM called "Community Source." Analyzing data gathered from multiple sources reveals that IOS adoption facilitates participatory reuse by enhancing information sharing and leveraging of broader community skills. Participatory reuse manifests itself when potential reusers participate in the entire development process leading to the creation of reusable assets. Based on data, we develop a theoretical model to illustrate how IOS affects reuse. While furthering research on IOS and reuse, the model informs managers wishing to foster participatory reuse that they are wise to adopt IOS as a vehicle to promote greater openness of the software development infrastructure for leveraging broader community skills and enhancing information sharing among projects' stakeholders.