Thats sounds like a derivative work to me.
From the US Copyright Office website:
http://www.copyright.gov/circs/circ1.html
WHAT IS COPYRIGHT?
Copyright is a form of protection provided by the laws of the United States (title 17, U.S. Code) to the authors of “original works of authorship,” including literary, dramatic, musical, artistic, and certain other intellectual works. This protection is available to both published and unpublished works. Section 106 of the 1976 Copyright Act generally gives the owner of copyright the exclusive right to do and to authorize others to do the following:
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To reproduce the work in copies or phonorecords;
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To prepare derivative works based upon the work;