Well I think I officially give up on Pluto actually supplying a source tarball ever again.
What truly amazes me is the lack of response to the issue. I would have assumed they read the GPL given they decided to license most of Pluto under the GPL. Just in case there's someone reading who cares about obeying the terms of the license here's an exert from section 3 - the last paragraph.
If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.
Binaries are provided through http and ftp in tar.gz, .zip and .deb form. The license you decided to distribute under requires that you provide source code through equivalent access. Subversion is not, and never has been, equivalent to either ftp or http. Nor is the format it transmits equivalent to a .tar.gz.
If you wish to claim to be an open source project then start by complying with the terms of the license under which you distribute.
I hope this catches the ears of someone who'll do something to rectify the situation.