I believe the '05 leads one to believe that a listed product is required.
Maybe why the '08 made such changes.
From the '08:
250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes.
(C) Metal Boxes. A connection shall be made between the one or more equipment grounding conductors and a metal box by means of a grounding screw that shall be used for no other purpose, equipment listed for grounding, or a listed grounding device.
I don't see where the screw needs to be listed, just the other two.