The same copyright laws apply whether the pattern is sold or available for free. The designer has the only right to decide what he or she wants to do with the pattern; i.e., sell it or give it away. Quite often the freebies are an enticement to get people to visit websites. Say if 1 person made 50 copies, kept 1 for herself & gave away the other 49 that is 49 people who had no reason to visit the website therefore costing the designer potential sales.
One thing I am so happy to see finally being addressed is whether or not someone has a right to sell the 1 quilt they made from a purchased pattern. I have always vehemently defended my right to do so since it is my property under the fair use doctrine. If I found a pattern I wanted to duplicate numerous times for the purpose of selling the quilts that would be another story.