I ran into an issue when I started selling Christmas stockings and after checking with a lawyer on it, as long as there is at least 5% difference between the item I created and the item the other person created it is considered unique. I had a problem with someone copying my work exactly for resell not personal use. All it took was a letter from my lawyer and they changed their work slightly and there was nothing else I could do. This all took place in 2008 so things might have changed since then but we haven't had any more problems.