This paper highlights the importance of community governance for ensuring the sustainability and robustness of open source projects. By analyzing 637 GitHub repositories, we trace the transition from founder-centric to shared governance. We analyze GOVERNANCE.md files to extract institutional roles, behaviors, and normative signals. Using a semantic analysis pipeline, we categorize these roles and behaviors into types, analyzing the growth in governance scope and differentiation over time. Our findings reveal that as the transition to community governance matures, projects tend to regulate ecosystem-level relationships and clearly define project oversight roles. This study provides a scalable pipeline for tracking the growth and evolution of community governance systems within the founder-centric framework of open source software.