I've been designing for 27 years, and have had to familiarize myself with all of this stuff. I see a couple of things in these threads that worry me.
Copyright doesn't need to be complicated for most people. If you are using someone else's work (be it patten, quilt, or picture of either) - they created it, and it is theirs. I respect their wishes or don't use it if I disagree. Very simple. Re-creating it in EQ, changing a few things, calling it inspiration - doesn't matter, and doesn't change the reality that it is based off of someone else's work. It just shows why designers are becoming more serious about protecting their work. I keep seeing 'who will know' and 'let them sue.'
Copyright is complicated for those trying to protect their work - it can easily get out of the artist's control and cause them to involuntarily loose their rights. One very real aspect of this is people showing quilts at shows and not properly crediting the designer - allowing others to think it is completely their work. We have to diligently defend our copyrights to keep them because of the very 'borrowing' and attitudes that have been detailed in these threads.
I have never seen or heard of a designer being unreasonable when approached about having a quilt shown in a quilt show. Permission to copy for 'guild use' or other uses is dangerous territory - it can so easily be misused. Some quilters are ruining it for everyone.
I believe that we are seeing more public domain blocks used because, quite frankly, a truly original design is nothing more than a headache, and more designers are keeping them to themselves rather than fight with all this. I know I am.