What's a good non-UNIX open-source operating system that's useful for day-to-day work, or at least academically significant enough that it's worth diving in to?

Here's a list of alternatives I put together to see some capabilities or traits UNIX lacked:

https://news.ycombinator.com/item?id=10957020

I think, usable day-to-day, I'd say you're down to Haiku, MorphOS, Genode, MINIX 3, and/or A2 Bluebottle. Haiku is a BeOS clone. MorphOS is one of last Amiga's that looks pretty awesome. Genode OS is a security-oriented, microkernel architecture that's using UNIX for bootstrapping but doesn't inherently need it. MINIX 3 similarly bootstrapping on NetBSD but adds microkernels, user-mode drivers, and self-healing functions. A2 Bluebottle is most featured version of Oberon OS in safe, GC'd language. Runs fast.

The usability of these and third party software available vary considerably. One recommendation I have across the board is to back up your data with a boot disc onto external media. Do that often. Reason being, any project with few developers + few users + bare metal is going to have issues to resolve that long-term projects will have already knocked out.

Minix isn't bootstrapping on netbsd, the entire goal of the system is to be a microkernel based unix. It uses the netbsd userland because you don't need to rewrite an entire unix userland for no reason just to change kernels.

Mental slip on my part. Thanks for the correction. I stand by the example at least for the parts under NetBSD like drivers and reincarnation server. Their style is more like non-UNIX, microkernel systems of the past. Well, some precedent in HeliOS operating system but that was still detour from traditional UNIX.

https://en.wikipedia.org/wiki/Helios_os

SqueakNOS? http://squeaknos.blogspot.com ;-) It has a native TCP/IP stack in Squeak.

The difference is PharoNOS has a Linux running behind while the idea of SqueakNOS is to build a complete operating system via Squeak. In this way you can quickly hack it. There is a great page about these initiatives here: http://wiki.squeak.org/squeak/5727

BTW, prior to SqueakNOS we implemented this: http://swain.webframe.org/squeak/floppy/ (using Linux and modifying Squeak to work with SVGALib instead of X) in just 900mb inspired in QNX Demo Disk: http://toastytech.com/guis/qnxdemo.html

I was going to mention QNX Demo Disk in my UNIX alternatives comment. I think I edited it out for a weak fit to the post. It was an amazing demo, though, showing what a clean-slate, alternative, RTOS architecture could do for a desktop experience. The lack of lag in many user-facing operations was by itself a significant experience. Showed that all the freezes and huge slow-downs that were "to be expected" on normal OS's weren't necessary at all. Just bad design.

It's neat that it was the thing that inspired one of your Squeak projects. Is SqueakNOS usable day-to-day in any console desktop or server appliance context? Key stuff reliable yet?

We implemented SqueakOS while some friends implemented SqueakNOS. I don't think they are being used anywhere but for educational purposes it is amazing that drivers and a TCP/IP stack could be implemented (and debugged!) in plain smalltalk. There was some more information here: http://lists.squeakfoundation.org/pipermail/squeaknos/2009-M...

There's GNU, which is by definition not UNIX. ;)

I'd assume that depends on your measure of worth, I'd say. Many operating systems had little academic significance when it was most academically or commercially fruitful to invest time in. Microkernel and dependency specific operating systems would be interesting. Or hardware based capability based operating systems.