I imagine that quilts are much like paintings, I can sell my original paintings, but should I copy someone elses painting and sell it, then I could be done for copy right. If I painted a painting copying someone elses work and gave it away then I can't be done for copy right! If you gave your quilt away to a charity or family member then you are not going to be done for copy right. (It only comes into play when you are selling the item concerned, for money and/or at exhibition level you would only want to be 100% original wouldn't you!.) I hope to make my own designs too one day, it is difficult to be 100% original as so much has been done before and we are of course influenced by what has come before us. As I do with my paintings, I keep well ahead of current trends etc by doing a lot of reading and research about my chosen field.
For my quilts, I use patterns and ideas from books etc that have been published especially for use of their patterns, then that way the original designer has given permission for others to copy her patterns, you can't go wrong doing that!
Some designs are very old and no one knows now who the original creator was unfortunately.
I have been working on a series of paintings only to find someone else has done a similar kind of theme, it happens all the time!
Gal