MultimediaKit provides common backend engine to play multimedia stream.
Currently, it supports mplayer backend based on MPlayerOSX.

MPlayer and MPlyaerOSX: http://www.sonappart.net/gnustep/mplayer/
MPlayerPort: http://www.sonappart.net/gnustep/mplayer/

WWW: http://www.etoile-project.org/