I've never bought a pattern. I look at it, draw a picture of it that's close enough and go with that. I've never copied what I drew and sent it to anyone. It would really have to be something I wanted badly enough that was really complicated before I would buy it. If that is a violation well then I'm guilty, but I don't plan on stopping anytime soon.
Really I think some of this is silly. If I were to put my time into something to copyright it is going to be something that someone can't duplicate by pushing a few buttons. Otherwise its like playing whack a mole to try and keep people from redistributing it.