On the gtk-doc-list mailing list, Matthias mentioned that the GraphViz license has been changed to the CPL (the same license as used for Eclipse), which is considered Free by both the FSF and OSI (although still GPL incompatible). This should remove the barriers that prevented it getting packaged by Linux distributions.

Due to the previous licensing, RMS urged developers of GNU software to not even produce output in the form that the GraphViz tools use as input. Maybe that can change now. While the license is GPL incompatible, the GraphViz tools can easily be invoked from the command line, passing a .dot file in, and getting output in PNG, PS, SVG, etc format (or even another .dot file with the layout information added), which is enough for pretty much all uses of the tools.

One of the features I added to JHBuild fairly early on was the ability to dump the dependency tree for a set of modules in the .dot format. So to visualise the dependencies for Gnome, you could run a command like this:

jhbuild dot meta-gnome-desktop | dot -Tps > gnome-2.10.eps

(of course, given the number of modules that are needed to build the entire Gnome desktop, you might get a better picture by picking a smaller number of modules).