For most quilt patterns, it is the written words and pictures that are protected by copyright, in other words the pattern itself (not the design). Most quilt designs are not themselves sufficiently original to be protected by copyright. (Notice I said MOST, not ALL.) IMHO, if you feel that you are copying someone, it is nice to ask them if they mind. Chances are that they will be flattered, and you won't wind up feeling somewhat guilty later.