The proliferation of open-source software development platforms has given rise to various online social communities where developers can seamlessly collaborate, showcase their projects, and exchange knowledge and ideas. GitHub stands out as a preeminent platform within this ecosystem. It offers developers a space to host and disseminate their code, participate in collaborative ventures, and engage in meaningful dialogues with fellow community members. This dissertation embarks on a comprehensive exploration of various facets of software development communities on GitHub, with a specific focus on innovation diffusion, repository popularity dynamics, code quality enhancement, and user commenting behaviors. This dissertation introduces a popularity-based model that elucidates the diffusion of innovation on GitHub. We scrutinize the influence of a repository's popularity on the transfer of knowledge and the adoption of innovative practices, relying on a dataset encompassing GitHub fork events. Through a meticulous analysis of developers' collaborative coding efforts, this dissertation furnishes valuable insights into the impact of social factors, particularly popularity, on the diffusion of innovation. Furthermore, we introduce a novel approach to computing a weight-based popularity score, denoted as the Weighted Trend Popularity Score (WTPS), derived from the historical trajectory of repository popularity indicators, such as fork and star counts. The accuracy of WTPS as a comprehensive repository popularity indicator is assessed, and the significance of having a singular metric to represent repository popularity is underscored. We delve into the realm of code quality on GitHub by examining it from the perspective of code reviews. Our analysis centers on understanding the code review process and presents an approach rooted in regularity to foster superior code quality by enforcing coding standards. In the concluding phase of our research, we investigate the intricacies of communication within technology-related online communities. Our attention is drawn to the impact of user popularity on communication, as elucidated through an examination of comment timelines and commenting communities. To contextualize our findings, we compare the behavioral patterns of GitHub developers and users on other platforms, such as Reddit and Stack Overflow.