At various times up to and including May 31, 2008 many people wrote:
Many things that I have snipped.
There appears to be a serious misunderstanding of the difference between copyrights and patents. If I implement an idea and it is found to be sufficiently similiar to a pre-existing patent, then I am in violation of that patent even if I am unware of its existence. If I create a work that is found to be similar to a pre-existing copyrighted work, my ignorance of that work is a perfect defense, as I am not violating the other creator's copyright even if my created work is found to be identical.
Now as to the GPL issue, the only mechanism that I can use to prevent another party from distributing my GPL covered work, is via the method of asserting my copyright against that party. Without the mechanism of copyright, I have no other avenue to compel their compliance with the terms of the GPL.
Thanks, -- Hal