This is being developed as part of the Octave project so subscribe to the [http://www.gnu.org/software/octave/get-involved.html maintainers mailing list]. When you checkout the Octave repository, you'll find the GUI source on the development/default [http://hg.savannah.gnu.org/hgweb/octave/branches branch].
You may also read [http://octave-gsoc2012.blogspot.ca/ Jacob's blog posts about the topic.]
==I'm having problem XXX using GUI Octave, XOctave, QtOctave, etc?==
Install Octave only, without any of the non-supported by GUIs and see if the problem disappears.