CVS Access
If you want the most recent source that has not been released, you can get it via Source Forge's CVS server. You will need CVS, if you do not have already. Then type the following at a command prompt in the directory you want to download the source to. When prompted for a password use anonymous. I know the font is small, but the command line is very long. You can just copy and paste it directly to your console.
cvs -d:pserver:anonymous@cvs.demeter.sourceforge.net:/cvsroot/demeter login
cvs -z3 -d:pserver:anonymous@cvs.demeter.sourceforge.net:/cvsroot/demeter co demeter
cvs -d:pserver:anonymous@cvs.demeter.sourceforge.net:/cvsroot/demeter logout
That's it, you should not have the most recent source. Keep in mind that this source has not been released. Even though we do our best to make sure everything checked-in is working. We can not make any promises to that, or if the test cases are testing correctly. Use at your own risk.
If you prefer, you can browse the CVS tree through its web interface.