If you were around in the late 1990s, you might have heard of former Apple exec Jean-Louis Gassée’s startup Be. Be Inc started out making its own hardware, then ported to Apple’s Power Macintosh hardware, then to x86 and then, after a few final struggles, went under and was bought out.
You can still download the evaluation version of the final release, BeOS 5 Personal Edition, but it was built for tail-end-of-the-’90s hardware, so it’s a bit dated today.
However, its spirit lives on in the form of Haiku, a from-scratch FOSS reimplementation which runs the original Tracker desktop and some of the handful of BeOS 5 apps. It’s one of the most polished and modern-looking alternative OSes out there, too.