In this article, we argue that the lack of theoretical definition in the literature related to open-source governance opens the floor for multiple possibilities to define it. Therefore, the existence of a baseline to refer to a robust governance solution is deemed crucial. We posit that defining vertical product domains as a benchmark to measure governance solutions robustness helps in theory advancement in governance literature. The creation of vertical product domains is the output of successful open-source projects due to the transformation of open sourcing. We develop a conceptual understanding to precisely define the vertical domains in open-source projects and future agenda for open source governance theory advancement.