Doom uses a fictional corporation abbreviated as “UAC:” this is trademarked by id Software and cannot be used in Freedoom. Instead, use the initials “AGM” for Freedoom.
What’s AGM stand for?
Anion Gerospace Morporation
“Awesome game, man.” perhaps.
Anthropogenic Global Mourning
Too real, man. Too real. 😞
From this comment from this 2009 doomworld forums thread:
It was an in-joke, and don’t feel bad for not understanding it completely… I don’t really get it either :P
If you were wondering just in case of writing a story or some such, I doubt anyone would care if you re-define what the letters AGM mean.
In 2017, an issue has been open on GitHub, and a related freedoom forum thread was started with a poll.
Someone has then proposed a back story in 2018, in a separate doomworld forum thread, calling it
Advanced General Mechanics
Finally, last year, a new doomworld forum thread asked the age old question once again.
Personally, however, I would give it the meaning:
###Applied Genetics Manufacturing
(I also thought of “Apex Genetics…”, but I dunno, it sounds more sci-fi, but also a lot more gaudy)
Edit: funny enough, the domain agm.earth is available to purchase, and isn’t even prohibitively expensive (USD 30.36 to register and renew).