Camelot
DFII prior to 6.1 used Motif toolkit (not sure which implementation, see
http://www.opengroup.org/motif and http://www.openmotif.org/), and from 6.1 on switched to Qt
(http://trolltech.com/products/qt ; Cadence is cited on their webpage).
Other popular toolkits include GTK+ (http://www.gtk.org) and WxWidgets (http://wxwidgets.org).
Stéphane
thank you Stéphane!
Camelot