Source code for the latest release of Spasmos can be found on the Sourceforge page.
If you need the latest and greatest version, grab a Subversion client and use the following incantation from a terminal to get the 'trunk' version:
svn co https://spasmos.svn.sourceforge.net/svnroot/spasmos/trunk spasmos
You can access the Sourceforge subversion repository here, or you can peruse the code without retrieving it.
Instructions for installing Spasmos can be found here.