There are several way to get the source code of abx.
The easiest one consist in downloading the prepacked version of the program from this site or from one of the Sourceforge.net mirrors.
However, if you are a developer and want to contribute to the coding phase of abx, you may be interested in the SVN repository.
The SVN repository is located at http://abx.googlecode.com/svn/trunk/, hosted by Google code.
To checkout the current release and get up-to-date, use
svn checkout http://abx.googlecode.com/svn/trunk/ abx
To develop, discuss, partecipate go to the developers' page.
Releases before 0.1 have been tested privatly and are not available, unless explicit request by a single.