I wasn't suggesting to automatically copy infos from gmap to osm but to provide something like a notification that the two maps differ in a place/road.
So, i understand that i can't create an automated list that lists what are the differences between gmaps and osm.
I would advise against comparing, too. A good lawyer could prove that diffs between the maps are made from Google's content. In short: unless it's explicitly whitelisted (e.g. Bing Aerial is on the whitelist, Bing Maps is not), avoid.
So, i understand that i can't create an automated list that lists what are the differences between gmaps and osm.