Into openstreetmap there is a gps tracks section. The tracks are recorded from users directy on the ways. The other users can also download its and use for your travels, especially for mtb and foot.
Suppose that I want suggest a trip and comment it, but I haven’t a complete gps track.
If into OSM there is the complete path, I could trace it (with josm or http://bikeroutetoaster.com/)) and save into new TRIP MAP section.
Any TRIP could have tag like mtb, foot, bike , “extract from map”/“recorded with gps” and other.
The purpose of uploading GPS tracks to openstreetmap.org is to assist with editing the map. It is not intended to be used for sharing tracks with others. So it would not be useful to upload tracks that have just been traced from a map.
If you want to share tracks, there a plenty other websites that let you do that, and have the option of an OpenStreetMap background. eg just use Bikeroutetoaster, as you mentioned.
Or see other websites in this list: http://wiki.openstreetmap.org/wiki/Track_drawing_websites