From http://www.cni.org/Hforums/cni-copyright/1997-03/0121.html "If an altered work is substantially similar in any significant part of its protectable expression, it is an infringement (unless there is an applicable defense, such as fair use). "Substantially similar", "similar in any significant part," and "protectable expression" are all terms notable for their ambiguity and context-specific nature. I do not believe there are any "guidelines" on how much must be changed, though I have heard many myths to this effect." Mark Lemley Assistant Professor, University of Texas School of Law Of Counsel, Fish & Richardson, P.C. mlemley@mail.law.utexas.edu