I worked for a needlework store part-time. The owner was very adamant about copyright, as in she would go ballistic if we owned a book of patterns but then we copied a pattern for someone else without them buying the same pattern. I agree that it is important for the independent artists get something for their creations, but it only applies to the pattern.
For the most part the only reason they are so "strict" is for the companies that want to go out and mass produce their products without giving them any credit (or money).
Copyright law only covers the original work (exact fabric brand, material, color, stitches, etc.), it does not cover the ideas or creative process. That's why a lot of software companies and others are going to patents instead. Copyright only lasts the author's life plus 50 - 70 years, so if you can find a pattern older than that, it is public domain. You also can't take something that is public domain and "copy right" it. (I'm going through this class right now for school).
A good rule of thumb is to change the pattern by at least 30 - 50%, most times this is enough to make it unique and one of a kind. PM me if you have any further questions and I will try to be more specific.
Happy Quilting