This is something that has bugged me for a long time... and here it is, broken down into pretty simple terms. I know a lot of people aren't going to like it much, but here it is:
Patterns And How They Are Affected By Copyright Law or, Debunking The Lies Told By Pattern Manufacturers
Now, when I have purchased patterns, if it says not to make something for resale, I never have, out of respect for the maker of the pattern... but really, you can't tell people that.
I'm posting this not as a "Hahaha, I'm going to go crazy making stuff to sell from your patterns!!" (because really, why would I? I'd rather make my own patterns for the stuff I sell!)... I'm posting it because I really think that everyone who sells patterns should sit down and read this, and really consider whether or not they want to be selling their patterns.