I had this problem one time. I tried to buy a pattern I wanted but no one had it. It sounded as if it was out of print. I made the quilt from the catalog picture, I used different fabric/color. About a year later the pattern started showing up again. I felt a little guilty. After thinking about it, I decided, If you are not selling, I think it is okay to copy if you have the ability. There are so many free quilt patterns out there now. I would buy a pattern if it was unique. Actually I have bought a lot of patterns and books, they rival my stash.
Some of the off the rack clothes are copies of designer clothes and it seems to be an accepted practice. What's the difference?