There is one other option for forest paths - Strava have made available their GPS heatmap for editing OpenStreetMap:

http://labs.strava.com/heatmap/

http://strava.github.io/iD/

So, depending on where you live, you may find local trails are on there (although you've still got to go in person to confirm they do actually exist, and to know exactly what they are - mountain bike trails, or narrow footpaths, or wide tracks for horses and 4x4s). In theory, it means you can shift effort away from sorting out gpx tracks, and more into getting the contextual information correct.