Almost 20 years-worth of content will be removed.
#Nintendo Issues Takedown Against Garry’s Mod https://www.thegamer.com/nintendo-issues-takedown-against-garrys-mod-after-18-years/ @thegamerwebsite
From the horse’s mouth: https://steamcommunity.com/app/4000 @steam
TL;DR: it’s not all Garry’s Mod content, just content made using Nintendo IP. Everything from just straight-up adding Nintendo characters to other games (apparently including a lot of Animal Crossing characters) to levels or parts of levels being brought from Nintendo’s games into other games.
@jqubed 😁 That’s good because Gary’s Mod has a lot of fans.