OpenStreetMap licence?

In general, the commercial map companies have identified copies of their maps by adding information for things that don't exist, such as fictional cities or cul-de-sacs that don't exist (depending on map scale). The maps might not be quite to scale, or other things that allow the map company to identify verbatim copies without disturbing people looking for legitimate things. My favorite was the Beat OSU in a Michigan map (a local sports rivalry). This is the same type of thing that phone books use to identify copies.