I, too, have added a lot of trail information to the Open Street/Bike Maps by taking GPS ride files, overlaying them on the OSM New Jersey map using the Potlatch2 editor (a little kludgy, but overall pretty easy to use), then tracing the trails that I've been on (they're "correct" to the level of accuracy that my GPS was able to obtain on the days that I rode the trails, and the accuracy of my tracing them). I've added content to Allaire, Clayton, Six Mile, Frost Woods, Rutgers Ecological Preserve, Huber and Hartshorne Woods, Round Valley (only made if half way around), Chimney Rock/Washington Valley, Voorheis, Lewis Morris, The Tourne, Allamuchy Deer Park, and Kittatinny Valley. I can't vouch that I've hit the entire trail system at these locations, but I keep adding content when I find that I've ridden on something new. I also haven't been to the southern and northernmost NJ venues, yet.
The OSM maps seem to take up to a month to reflect newly-added content in the downloadable maps. I use a Garmin 705, and the trails aren't usually visible until you zoom in to scale 500 feet or less. For those of us with older GPS devices, this could be trail map option.