Open source software (OSS) development is a community-oriented, network-centric approach to building complex software systems. OSS projects are typically organized as edge organizations lacking an explicit management regime to control and coordinate decentralized project work. However, a growing number of OSS projects are developing, delivering, and supporting large-scale software systems, displacing proprietary software alternatives. Recent empirical studies of OSS projects reveal that OSS developers often self-organize into organizational forms we characterize as evolving socio-technical interaction networks (STINs). STINs emerge in ways that effectively control semi-autonomous OSS developers and coordinate project activities, producing reliable and adaptive software systems. In this paper, we examine how practices and processes enable and govern OSS projects when coalesced and configured as contingent, socio-technical interaction networks. We draw on data sources and results from two ongoing case studies of governance activities and elements in a large OSS project.