Free/open source software users were previously responsible for managing the challenges associated with their software themselves. Recently, a new generation of entrepreneurs seized this emerging market opportunity by positioning themselves as service providers for free/open source software users. Conceptualizing such providers as “institutional entrepreneurs,” we find that due to the nature of the free/open source software context, they exhibit a different set of legitimation actions compared with similar efforts in other contexts. Based on our empirical analysis of free/open source software service providers and drawing on prior theory, we identify two entrepreneurial actions aimed at gaining legitimacy specific to the free/open source software context, namely, product-based theorization actions and evangelization actions. We also demonstrate that institutional entrepreneurship is shaped by the nature of free/open source software products and the openness values at the core of the free/open source software movement. Our work hence underscores the importance of the context of institutional entrepreneurship.