Unlike most game mods (which are, to my knowledge, a distribution of a copy of modified game software), I'm writing a small desktop application which allows users to make their own custom changes (modifications/mods) to (their own copy) of the game by using the app.
The app will make a copy of some of the game's files (that they have) and then modify those copies. 0% of the app is, in of itself, copyrighted material (the game's code, etc.). I am writing this application from scratch. It is 100% my own creation.
In addition, it doesn't contain any logos, images, etc., from the game, and am I not planning on naming it anything which would make others feel that the application (or I) am associated with the game's publisher (or developers).
Edit 1: I figured out how to modify this game by manually sorting through (and figuring out) gibberish with a hex editor. (I did not decompile the game's files to see the original source code.) My application primarily makes hex edits.
Assuming that all of how I described the application above is true, if I distribute it on the internet free of charge, would there be any possibility of any potential copyright infringement, lawsuits, complaints, etc., from the game's publisher or developers to your knowledge?
Can they possibly "get me" for distributing my own software for free, even if my software literally doesn't contain any of their property (despite having the capability to modify their property)?
By my understanding of articles like this, https://hackerbot.net/faq/54-are-game-hacks-legal, I may be in the clear. But articles like this https://mttlr.org/2012/11/gaming-mods-and-copyright/ make me feel like maybe I shouldn't have started hacking games to begin with!
I am aware of issues with using game mods/hacks to get an unfair advantage in online competitive environments.
The primary purpose of my software is NOT to give an advantage in competitive online gaming, etc. It's merely to enjoy the game and play it causally. (Bring life back to a mostly abandoned game.)
It can technically be used to get an advantage with gameplay. Although I highly doubt this will ever be an issue (of the only two online competitive gaming platforms that I'm aware of, I am a moderator of one of them, and know the moderator of the other one), should it be that, in order me to avoid facing any consequences for distributing this software, it is necessary for me to make my app put a "watermark" of some kind in the modified copy of the game which it makes, let me know!
Edit 2: (Question 2) (This edit is a result of Neil Meyer's comment about the specific EULA of the game in question.)
The EULA of the (1999 PC) game in question, states (among other things):
You may not copy the Software (except as specifically permitted herein) and, except as expressly permitted by law, you may not modify, translate, reverse engineer, decompile, disassemble or create derivative works of the Software.
Clearly they do not permit copying the game (which I am not). I am therefore zeroing in on the clause:
except as expressly permitted by law
Does this mean that, if it's legal in the country where I live, then they (the publisher) do not object if I provide users (who also live in a country where it's legal to modify PC games) a means to modify this PC game?