The City of Munich has a long open source history. We have been using open source products and frameworks in both infrastructure and software development since the turn of the millennium. We reached a new level of our open source development in 2021 when our city council decided that all open source in-house developments would be made publicly available - according to the principle of public money - public code. With our presentation, we would like to show what the success factors for open source development are, what advantages it has and what legal and organizational requirements we had to create for this.