The source code of phpList is managed using Subversion, hosted at Sourceforge
More information can be found at the sourceforge phplist pages
To get the latest sources working, you need to check out in two stages: funny sayings
go to the directory where you want to place your local copy and type
svn co https://phplist.svn.sourceforge.net/svnroot/phplist/trunk/phplist/ phplist cd phplist/public_html/lists/admin/ svn co https://phplist.svn.sourceforge.net/svnroot/phplist/branches/languages-utf8/lan/ svn co https://phplist.svn.sourceforge.net/svnroot/phplist/branches/languages-utf8/help/ svn co https://phplist.svn.sourceforge.net/svnroot/phplist/branches/languages-utf8/info/ cd .. svn co https://phplist.svn.sourceforge.net/svnroot/phplist/branches/languages-utf8/texts/
Currently the FCKeditor hasn't been ported over from CVS to SVN and I'll update instructions for including it, later.
The above will check out the code as an "Anonymous User" and you will not be able to write back to the repository. In order to check out as a developer, you need to tell your Subversion tool to use a username and password.
Sourceforge has a list of recommended software but my tool is not listed. I use smartSVN. Not opensource, but very powerful.http://goo.gl/PKsQv