This study presents an initial set of findings from an empirical study of social processes, technical system configurations, organizational contexts, and interrelationships that give rise to open software. "Open software", or more narrowly, open source software, represents an approach for communities of like-minded participants to develop software system representations that are intended to be shared freely, rather than offered as closed commercial products. While there is a growing popular literature attesting to open software [DiBona, Ockman, Stone 1999, Fogel 1999], there are very few systematic studies [e.g., Feller and Fitzgerald 2000, Mockus, Fielding, Herbsleb 2000] that informs how these communities produce software. Similarly, little is known about how people in these communities coordinate software development across different settings, or about what software processes, work practices, and organizational contexts are necessary to their success. To the extent that academic research communities and commercial enterprises seek the supposed efficacy of open software [Smarr and Graham 2000], they will need grounded models of the processes and practices of open software development to allow effective investment of their resources. This study investigates four communities engaged in open software development. Case study methods are used to compare practices across communities.