See http://rudd-o.com/monopolies-of-the-mind/thoughts-after-my-d...:
"Richard is against abolishing copyrights because, to his view, without copyright, enforcing copyleft would be impossible."
Copylefting a project says to the world that we value freedom more than compensation. It's the right message but depends on the wrong "logic" of copyright. Ideally, we would all reward companies that value freedom above profits, thus ensuring that freedom is profitable. But for now, copyleft exists as a strong-arm tactic against the over-protection of information. In the sense that copyleft utilizes copyright law to enforce freedom, it's hard to say whether GPL or other open source licenses have a greater respect for freedom.
There would have to be some other enforcement mechanism to prevent this for Stallman to be happy. He may not think that's possible, but I'm sure he would be happy to be proved wrong.
I think that a post-copyright regime could easily require code exposure for computers that are sold to consumers - that's far less radical than a post-copyright world would have already been in order to abolish the stuff.