Sustainable Open Source Software (OSS) projects are characterized by the ability to attract new project members and maintain an energetic project community. Building sustainable OSS projects from a nascent state requires effective project governance and socio-technical structure to be interleaved, in a complex and dynamic process. Although individual disciplines have studied each separately, little is known about how governance and software development work together in practice toward sustainability. Prior work has shown that many OSS projects experience large, episodic changes over short periods of time, which can propel them or drag them down. However, sustainable projects typically manage to come out unscathed from such changes, while other projects do not. The natural questions arise: Can we identify the back-and-forth between governance and socio-technical structure that lead to sustainability following episodic events? And, how about those that do not lead to sustainability?

From data of commits and email traces of 262 Apache Software Foundation (ASF) incubator projects, here we employ a large-scale empirical study to characterize episodic changes in socio-technical aspects measured by Change Intervals (CI), governance rules and regulations in a form of Institutional Statements (IS), and the temporal relationships between them. We find that sustainable projects during episodic changes can adapt themselves to institutional statements more efficiently, and that institutional discussions can lead to episodic changes intervals in socio-technical aspects of the projects, and vice versa. In practice, these results can provide timely guidance beyond socio-technical considerations, adding rules and regulations in the mix, toward a unified analytical framework for OSS project sustainability.