Copyright is a contract, and like any other contract is enforcable though a legal framework. I recommend reading Rothbard’s differentiation between copyright and modern patent protection. He clearly says that anyone copying (even if not the first buyer, and the good has been resold) is in violation of contract and would be prosecuted in an anarcho-capitalist legal system.
Secondly I would like to respond to the topic of business models. First read what I quoted from Mises (so you know where I am coming from), then I would argue that there is no (repeat: NO) business modle capable of making profits (not hobby money) that would justify creating an infinite good (which would fetch a 0 price on the market). Your FOSS example is such BS, I am truly sorry you hope that to become the norm in electronic development.
I would also argue that within an non-IP world there would be a complete disruption in the pricing mechanism in the development of Ideas - I may be way off course here, but I am now convinced that the entire “infinite goods” market will fail in the same way socialism would- due to there being no market signals as to where and what to focus resources in idea development (this is due to the disconnent between before and after the good becomes in infinite supply). Of course, just like socialism there is the illusion of a market price (your “business model”) which would include advertising or perhaps a rate of consumer ownership (ie. downloads, etc), but the profit motive in missing (unless you count the socialistic concept of recognition as reward enough) . What I am trying to say is the main thesis of Mises’ “Socialism”, that without proper pricing signals, consumer demand will not be met and the system will ultimately fail. This is, I suspect, why Mises supports the monolpoly pricing of ideas, and Intellectual Property, in Human Action.
Remember though, this is assuming a good of Infinite supply. So in reply, we are arguing the complete removal of IP (copyright, license keys, contract, patent, etc.)