I posed this question a few yeas ago to an Intellectual Property Attorney and this was her response:
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This is my question – can I purchase a pattern – any pattern – and make that product for resale.
Update 3/15/10: I called an IP (Intellectual Property) lawyer this morning and she said that what you make from patterns is not protected under copyright. All that is protected is the pattern itself. Sew forth and multiply.
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Unless the design is unique rather than common there are so many variations of the finished product the designer cannot make this statement. Think patchwork pattern, the "basic black dress", shorts or tank top patterns, child's sundress pattern. They all follow the same fundamentals but the outcome is different.