In reply to Andrew
"Entirely untrue - all Open Source (and Free Software) licences, including the GPL, depend on enforceable copyright. "
Open source is copyright free in the sense that anyone can freely make copies of it and amend it for their own purposes. That is what I meant. I agree that the licence also places restrictions on what can subsequently be done with those copies, so the granter of the licence still retains the right to enforce that!