FreeBSD, Haiku, and other systems everyone mistakes for Linux are actually their own OS outside of the system that you are used to.
Looking for non-Linux open-source options? From ghosts of past operating systems to fascinating works in progress, here are my top picks.
FreeBSD and Slackware are both outstanding OSes. FreeBSD is more UNIX-like, while Slackware is more Linux-like. One is geared for servers, while the other is a bit more general. FreeBSD and Slackware.