Builds fine now.  Thanks for doing this.  You may want to include the
following patch.

regards,

adrian.

Index: Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/graphics/graphviz/Makefile,v
retrieving revision 1.35
diff -u -r1.35 Makefile
--- Makefile    5 Jun 2005 22:29:07 -0000       1.35
+++ Makefile    6 Jun 2005 22:12:23 -0000
@@ -25,6 +25,10 @@

 .include "../../mk/bsd.prefs.mk"

+.if ${OPSYS} == "Darwin"
+BUILDLINK_DEPENDS.gd+= gd>=2.0.33nb1
+.endif
+
 CONFIGURE_ENV+=                TCLCONFIG=${TCLCONFIG_SH}
 CONFIGURE_ENV+=                TKCONFIG=${TKCONFIG_SH}
 CONFIGURE_ENV+=                X11PREFIX=${X11PREFIX} X11BASE=${X11BASE}