Here is how I analyze this. The software that runs the game is automatically copyright protected. The owner of a copyright is entitled by law to derived materials. I think your cheat sheet is a derivative.
To sell your sheet you must refer to the original by a name that is at least common law protected. And maybe more.
So your only way is work a deal with the owner to sell a product to help one learn the game, and split the money with the owner. After all, without the owner 's efforts you would have nothing to add to.
Others may see it differently but that is how i see it.
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You would need to look at the EULA for each individual game. Most have clauses where you agree not to cheat, and most probably have clauses where you agree not to enable others to cheat. Without having seen the EULA for your specific games, I couldn't tell you.
As to whether the publishers would have a copyright claim against you, a lawyer in your state can help you interpret the case of Galoob v. Nintendo (the Game Genie case) and any other relevant precedent.
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I don't think it's possible to do this legally. But I do think it's possible to create a literary work that offers advice on how to play the game, strategies, critiques of its design, etc.
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If I understand you correctly, you have an independent program XYZ residing in a separate section of RAM from game ABC once loaded, but which has calls from game ABC and feeds going to ABC (inputs from the game and outputs going to the game) all for the purpose of cheating game ABC. Deja vu' -- I recall using something like that years ago in online Scrabble - the independent program analyzed the tray letters and the board and came up with the highest scoring word to play so you could win an online multiplayer Scrabble game. It was fun for about 2 days and then got boring because I always won so there was no challenge and thus little further excitement. Plus other players knew I had to be cheating to get the best word every time in just a few seconds. I doubt separate program XYZ is a derivative just because XYZ interfaces with an program ABC, although the statutory definition in 17 USC 101 of a "derivative work" is extremely broad:
"A “derivative work” is a work based upon one or more preexisting works, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, art reproduction, abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted. A work consisting of editorial revisions, annotations, elaborations, or other modifications which, as a whole, represent an original work of authorship, is a “derivative work”. "
I think "interfacing with" is different that "based upon", although I would need to research the issue to be more certain.
Also, I am not so sure the use of the primary program name is not nominative use or descriptive use if done right. For example:Use the MAXIPLAY program to get maximum scores in Scrabble-type crossword games.[Note: MAXIPLAY is not the real name of the program, as I no longer remember it.] So, if logos and other indicia are avoided I doubt permission is needed, especially if a typical trademark disclaimer legend is used.
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