Yesterday, the Winamp source code, build tools, and associated libraries for the Windows app were published on GitHub, allowing anyone to provide bug fixes and new features to the iconic media player.
However, its license prohibits the distribution of modified software created through the release of this source code.
https://github.com/WinampDesktop/winamp
This is not open source. In open source people contribute to the project and in return the code belongs to anyone who likes to take it and work on it. Here they are asking for contribution while fully owning the code. It's basically free labor