GNU/Linux
From Mario Fan Games Galaxy Wiki
GNU/Linux, known colloquially as just Linux, refers to a family of free software operating systems utilizing the Linux kernel, and designed after the proprietary UNIX.
Its userbase has unjustly earned an occult reputation, and as such, outsiders tend to avoid GNU/Linux; few MFGGers run it on their systems. However, the most commonly known users of GNU/Linux on MFGG are onpon4, OniLink++, RetroX, Hohoo, and Techokami.