kicad sources can be found at:
http://kicad.svn.sourceforge.net/

Kicad repository uses svn.

If you want to get sources see:
http://kicad.sourceforge.net/wiki/index.php/Download

You must have subversion installed on your computer
run the following Subversion command:

svn checkout http://kicad.svn.sourceforge.net/svnroot/kicad/trunk/kicad kicad-sources
to install sources and docs in kicad-sources.

One can also dowload tarballs (without svn ) from:
http://kicad.svn.sourceforge.net/
tarballs are created "on the fly" in .tgz format (.tar compressed)
Stable versions are in tags, latest versions are in trunk/kicad