Nice analogy! One thing that has to be considered is that statements of ownership are easily disregarded if everyone involved knows about agreements to the contrary, but the real problem is where people who are not aware of (or party to) such agreements see such statements and are then thrown into confusion about the real status of the work in question.
It would be a bit like someone pulling a book of the shelf in the aforementioned purchaser's house, having been told by the purchaser to "take any of my books if you like them", and then reading the "property of man_ls" statement. One would be obliged to check once again with the purchaser or potential owner to make sure that the book is not one that has been borrowed and then mixed up with the rest of the purchaser's collection.
Such manual checking that everything is still legal or acceptable is precisely the kind of thing that conflicts with Free Software licences because one of the aims of such licences is to eliminate such bureaucratic obstacles, especially when they can be misused to effectively limit distribution even if grand promises of generosity have been made.