Historically speaking, open source has been woven into the culture of mainframes since their inception, with organizations meeting to collaborate on source code as far back as the 1950s. These communities have continued to collaborate through the decades since then, but with the rise of proprietary software and changing of the industry, the importance of open source software waned somewhat. In 2015 the renaissance of open source in the mainframe began with the launch of the Open Mainframe Project. This presentation will discuss the success of the Open Mainframe Project and explore the ecosystem of modern open source software available for the mainframe, from bash and git on IBM z/OS Unix System Services to Kubernetes on Linux for the IBM Z architecture.