Funny, the latest commit is "Removing code which is not open"[0], which means they are infringing on someone else's licensing terms by keeping it in the git history. [0] https://github.com/WinampDesktop/winamp/commit/0a4b7d32d0906...
Based on https://github.com/WinampDesktop/winamp/issues/11 it's their own code, just a different service they didn't decide to release the source for.
-dro