The success of open source software has been placing pressure on the business models of proprietary software vendors. In response, many software vendors have shifted from a paid-for license model to an open source business model. This presentation will explore the emerging trend of proprietary software vendors transitioning to an open source business model - the elimination of software licensing fees, source-code transparency, and a reliance on services as the revenue engine. It will cover the impact on software vendors and end users alike, and will include best practices from a number of companies that have already made the transition, including failed attempts.