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 our research we explore collaboration networks in the WebKit and OpenStack open-source projects, by mining their source-code version-control-systems data with Social Network Analysis (SNA). Our approach allows us to observe how key events in the industry affect open-source collaboration networks over time. With our findings, we highlight the explanation power from network visualizations capturing the collaborative dynamics of high-networked software projects over time. Moreover, we depicted that competing companies that market similar products in the same market, can collaborate in the open-source community while publicly manifesting intense rivalry (e.g. Apple vs Samsung patent-wars). After integrating our findings with the current body of theoretical knowledge in management strategy, economics, strategic alliances and coopetition, we propose the novel notion of open-coopetition, where rival firms collaborate with competitors in the open-source community. We argue that classical coopetition management theories do not fully explain the competitive and collaborative issues that are simultaneously present and interconnected in the WebKit and OpenStack open-source communities. We propose the development of the novel open-coopetition theory for a better understanding on how rival-firms collaborate with competitors in an open-source fashion.