The latest version of GMediaServer is 0.13.0, which was released on 10 November 2007. The source code can be found on http://download.savannah.gnu.org/releases/gmediaserver/gmediaserver-0.13.0.tar.gz.
GMediaServer has been packaged by Jochen Friedrich for Debian and is currently available in testing (Etch). The package is called gmediaserver.
This file, as well as older versions, are available in the GMediaServer file area.
A FreeBSD "port" is also available of GMediaServer. You can find the necessary files to build a package on http://www.uvm.edu/~jflemer/omnifi/gmediaserver-port.tar.gz.
The source code of GMediaServer is available in CVS on Savannah. See http://savannah.gnu.org/cvs/?group=gmediaserver for instructions on how to browse and retrieve the code.