Comment by chii

copyright doesn't give you the kind of rights that a GPL license does - which is not based on copyright, but on contract law (ala, it's in the name - licenses).

A sale of an object does not transfer those licenses (but those licenses are still valid on the seller - a manufacturer selling widgets will have to obey the GPL clauses. If an end user of this widget wants the source code, they have to go back all the way to the manufacturer, rather than any of the middle-men presumably).