Every now and then files are packed together and released as a tarball and an RPM package. Check the download page for the files.

You can get the bleeding edge version directly from the Sourceforge CVS

cvs -d:pserver:anonymous@cvs.xmmsd.sourceforge.net:/cvsroot/xmmsd login
cvs -z3 -d:pserver:anonymous@cvs.xmmsd.sourceforge.net:/cvsroot/xmmsd co xmmsd