However, there are legitimate ways to access historical versions if you already own the game, as well as community archives for the truly free early versions. Accessing Garry's Mod 11 (For Game Owners)

: Adds a massive array of electronics, sensors, and chips to automate your builds. PHX (Phoenix Model Pack)

Another loophole: if a friend has GMod, they can stream the game to you using Steam Remote Play Together. You join as a “virtual player” without owning the game. It’s not a permanent download, but you can play together for free.

Most non-Steam versions are restricted to single-player.

I opened the console to force a quit, but the text scrolling by wasn't code. It was a repetition of a single coordinate: 0, 0, 0 . I looked at the center of the map. There was a small, black cube that hadn't been there before. As I walked toward it, my speakers began to emit a low hum that grew into a scream. I pulled the plug on my PC, but the screen stayed lit for five seconds longer than it should have, showing a single message in the corner: “Validation Failed.”