The search for "GMod 11 non-steam" and "gmod without steam" has a long history. Forums and blog posts dating back to the early 2010s show players trying to bypass Steam's dependency to launch the game. These "Non-Steam" versions are essentially that have been cracked to run without Valve's client.
Downloading files from unauthorized third-party sites hosting "free cracked GMod" is highly dangerous for your computer. gmod 11 working non steam free
A precursor to the Steam Workshop that allowed players to download content directly in-game. The Transition: The search for "GMod 11 non-steam" and "gmod
During our testing, the game performed relatively smoothly, with minimal crashes or performance issues. We observed: the game performed relatively smoothly