Yes the Pine Barrens are legal, when we went down there we checked in with the park rangers to make sure it was legal. Beleive it or not you can "offroad" in ringwood state park. The rangers will let you drive in the park if you have a permit allowing you to either go to the model airplane field, hunt or participate in a trail clean up program. Also if i'm not mistaken the mystical offroading place in West Millford is off of Burnt Meadow road.
-Pete