I worked in publications for about 30 years. Copy editors were “salaried” and could not earn overtime regardless of how much they worked (and still are, most places); but if you go free-lance, you get paid by the page. This means the smart people did no overtime but moonlighted for other employers, whose copy editors were doing the same thing. It is kind of crazy, when you think about it. It would be a heck of a lot easier for the publishers just to pay overtime, and probably wouldn’t cost that much more, since they could hire fewer people, probably.