From the NRA site --
http://www.nraila.org/media/misc/nj.htm
"...no differentiation is made between carrying openly or concealed..."
... when referring to the need to have a concealed permit to 'carry', period.
Guns are taboo enough in NJ that someone openly carrying probably wouldn't get 10 feet without having the cops called on them. I live in the metro NYC area, not in the backwoods of NJ, so it would be quite a surprise to see someone openly carrying.