Die Brummbeere is an ownCloud audio player written based on the Qt framework. The application was written for embedded systems in mind, so it features a very simplistic user interface suitable for low resolutions and optimized for low energy consumption. It still runs on Linux and Mac. Windows is currently not supported due to a lack of audio streaming support from password protected locations on Windows. That might be fixed in future Qt versions.
You can read more about running Die Brummbeere on different platforms on its project website:
Die Brummbeere source code is distributed under the GNU GENERAL PUBLIC LICENSE Version 3.
Die Brummbeere documentation is Public Domain.