In an era of software crisis, the move of firms towards distributed software development teams is being challenged by emerging collaboration issues. On this matter, the open-source phenomenon may shed some light, as successful cases on distributed collaboration in the open-source community have been recurrently reported. In this paper, we explore the collaboration networks in the WebKit open-source project, by mining WebKit's source-code version-control-system data with Social Network Analysis (SNA). Our approach allows us to observe how key events in the mobile-device industry have affected the WebKit collaboration network over time. With our findings, we show the explanation power from network visualizations capturing the collaborative dynamics of a high-networked software project over time; and highlight the power of the open-source fork concept as a nexus enabling both features of competition and collaboration. We also reveal the WebKit project as a valuable research site manifesting the novel notion of open-coopetition, where rival firms collaborate with competitors in the open-source community.