it's hIDE using graphviz I think or dot something, I forget which is there a dot-something that generates graphs? it's from AT&T I think
hIDE is on sf.net
http://www.dtek.chalmers.se/~d99josve/hide/
http://ftp.gnu.org/pub/savannah/files/codeboost/codeboost.pkg/0.2.2/INSTALL
look at ATerm, Stratego, SDF, etc the MetaEnvironment might help