Eh, yeah, I guess there could be a debate about that. Technically, some court might find that any modification to a copyrighted work results in the creation of

Eh, yeah, I guess there could be a debate about that. Technically, some court might find that any modification to a copyrighted work results in the creation of a derivative work; but without distribution, it's pretty clearly fair use still I'd think. The most relevant case I know of is Lewis Galoob Toys, Inc. v. Nintendo of Am., Inc., 964 F.2d 965 (9th Cir. 1992). Nintendo sued sued the maker of Game Genie for contributing to infringement by letting people essentially edit their games in memory. The court said that just being in memory isn't a fixed medium for it to count as a derivative work, saying that editing something in memory was akin to shining a kaleidoscope on a painting and therefore not infringment. However, I think this requirement of a derivative being "concrete" is something the California judges largely just made up. But even if it was infringement, the court still said it was fair use because it was for a non-commercial purpose and couldn't have any negative effects on game sales, the 1st and 4th factors involved in fair use under 17 USC § 107.