Although a license like the GNU GPL or the various license available by the Creative Commons or even a simple license like the one in the Free Music Philosophy can make use of copyright law to achieve unrestricted distribution, that is a pragmatic position taken in consideration of the views of people who may wish to implement it.
For example, I do believe credit should be given where it's due; so I give it of my own free will and I appreciate it when it is given. But my feelings in this matter don't justify the use of the very system I oppose to cherry pick the freedoms that may be abridged and make this mandatory, a requirement. A system of licenses that require copyright law to be workable, and for enforcement, create yet another bureaucracy that may end up, in society's hands, worse than the current copyright one. I can't consistently argue for freedom and openness when the very thing I am against, copyright law, appears to be necessary for my freedom. I therefore have taken a more idealistic and extreme view in that all information I publish is freely copiable without restrictions.