If I did not miss anything graphviz is only used at compile time during docs generating. Looking at the latest masked ebuild an explict RDEPEND="" is missing.
fixed - thanks. Want this package? Need a version bump but otherwise its tame.
Sorry, this one isn't sold. :) I just checked all ebuilds depending on GraphViz for license issues because of bug 134575. The number of ebuilds in this short list with incorrect dependencies was very high, btw.. I just hope this is no sign for the overall quality of the tree...