I make the specification of non-linux because otherwise this would just become a thread full of obscure distros that do the same thing as a million other distros.
Some lesser known OSs:
- AROS - based on Amiga OS, has some derivatives like IcarOS and MorphOS
- Haiku - based on BeOS
- Redox - Unix-like, made in Rust (might technically count as linux?)
- Serenity - Unix-like, very late 90s look and feel
- Kolibri - Tiny OS, the image is ~44MB. It also has a smaller version that fits in a single floppy.
- PhantomOS - When 3 Russians decide to turn everything about a typical OS upside down.
“inspired by” would be more accurate. there’s no original BeOS code in Haiku for legal reasons (other than the interface, which was open-sourced with the release of BeOS 5). All backwards-compatibility with original BeOS software is (impressively) reverse-engineered. Haiku OS is, itself, original software made to - in every way - look, feel, and operate just like BeOS did.
edit: i had a buddy in high school who had a BeBox. it was like having the best of a Mac and a PC in one machine. it really was a spectacular machine and OS. i really wish Apple had picked it up, but they went with NeXTSTEP instead, which, i admit, was still a pretty solid choice.