Arif Bilgin, AT&T Research (smyrna and Windows support)
Don Caldwell, AT&T Research (map labeling)
John Ellson, AT&T Research (Tcl/Tk and codegen extensions)
Emden Gansner, AT&T Research (dot, neato, twopi, circo, fdp, osage, smyrna, gmap)
Yifan Hu, AT&T Research (sfdp, gvmap, cluster, mm2gv)
Stephen North, AT&T Research (dot, neato)

and

Yehuda Koren, Yahoo! Research (neato)
Vladimir Alexiev (codegen improvements)
David Dobkin (spline-o-matic)
Eleftherios Koutsofios, AT&T Research (dotty, lefty, spline-o-matic)
Bruce Lilly (pic driver)
Glen Low (Apple Mac OS X port, also the page icons on this site.)
John Mocenigo, AT&T Research (Grappa)
Jeroen Scheerder (allow URLs in PDF distilled from Postscript output)
Richard G. Daniel (RPM packaging)
Gordon Woodhull (Dynagraph)