Some sites have lots of designs that are free. You have to read everything and I just opt for the old/non-copyrighted ones. In any case, I don't sell mine so have little to worry about right now.
Also, if you alter a quilt and they can identify the source, then you can be in trouble. You really have to alter it a lot.
From another quilter here:
"If your pattern came from somebody else's pattern you saw it is still theirs--is the way I understand it. The IDEA came from 'their hard work....' ..."
Also, you do not have to get a copyright # on an item/idea whatever if you don't want to. The question is ONLY if you want to argue it and you have to prove you did it first.
And if you do register it with the patent office, you have the jump on someone but still have to prove it in order to sue or get compensation.
I think it is nuts. There is very little NEW under the sun anyway. Not that I think anyone and everyone should take and not give credit where credit is due. It's just that if you publish a book of patterns, then let people name their source and then, IMHO, sell it and claim with materials and work they did and their interpretation of the pattern.
Right now a friend of mine is having trouble with folks who download her images (photography) and share and do not link back to her so she gets credit and eventually payment for any image used. She has a couple images on Getty images and someone there sued Getty for a photo within a photo that was copyrighted...