Download the latest release tarball (1.5):
See http://mirrorbrain.org/files/releases/ for all releases.
All code lives in a Subversion repository which can be checked out with the following command:
svn checkout http://svn.mirrorbrain.org/svn/mod_asn/trunk/ mod_asn
The tree can also be browsed via ViewVC.
mod_asn binary packages are available from the same locations as the MirrorBrain binary packages; therefore, please look here: http://mirrorbrain.org/download/
Notes for packagers
mod_asn should be fairly trivial to package. You could look at the openSUSE spec file here, for rough guidance (click on the 'files' tab).