This article describes how one would download the sources.
Get the code
Ecopath6: ?https://sources.ecopath.org:8443/svn/Ecopath/trunk/Ecopath6
Ecopath5: ?https://sources.ecopath.org:8443/svn/Ecopath/trunk/Ecopath5
Click OK and enter your username and password
A WinCVS alternative to SVN would be RapidSVN but requires a pre-released version (9.9): ?http://www.rapidsvn.org/download/nightly/win32/