HubMiner
Sorry, I could not get back to this earlier...  How about following proposal: Please create an entry in Michigan wiki, outlining high level info about the S-2-S trail and its status; alternatively, there is OSM Task Manager [http://tasks.openstreetmap.us].

I agree with you on license points.  Someone would need to reach out to Up North Trails to get their approval.  From their ABOUT page [http://www.upnorthtrails.org/about.html] it sounds like they might be amiable to that.  

National Forest Service is probably ok, but they didn't have this trail on their interactive map.