For the past 15 years, I've been the author of Fluent Assertions, an open-source project with over half a billion downloads. Recently, I made the decision to commercialize it—a move I still stand by, but one that didn’t come without controversy. In this talk, I'll share the key lessons I’ve learned from maintaining a widely used library for so long. We'll discuss what makes a project successful, how to be a responsible maintainer, and ways to monetize an open-source project. I’ll also dive into the challenges of commercialization, managing expectations, and handling difficult (sometimes entitled) users.