This OS news poll only lists a handful, and doesn't bother to provide any helpful links, so I have done that below.
With the possible exception of OpenBeOS and Syllable/Atheos, there's nothing there that is particularly "different". Where are the real radical ideas, like a pure virtual memory OS that only uses disks as backing store or perhaps a "network os" where everything is packet based? Oh, well: maybe one of these will ring your chimes:
http://plan9.bell-labs.com/plan9
Bell Labs continues to dabble in a different Unix.
This is the famous OS that wasn't what Linux Torvalds wanted. It's author is the guy who carped about Linux and wrote the famous Operating Systems Design and Implementation books (I have an early copy around here somewhere).
Update: OpenBeos seems to be gone, but Haiku has picked up the flag.
This is an attempt to keep the BeOS alive as a desktop OS . BeOS once was desktop oriented, but closed down and sold everything to Palm. The distinguishing aspect of Be and OpenBeOS is their object focus. The whole OS interface is object based, which means you would program for it in C++ or some other object oriented language. See http://www.beatjapan.org/mirror/www.be.com/developers/developer_library/tutorials/approachingBe.html for more.
Pure assembly language (x86) all the way. Fits on a single floppy, yet boots as a GUI. Strongly focused on squeezing ultimate performance out of x86 hardware.
Another pure assembly language OS.
http://syllable.sourceforge.net/
Syllable is a fork of Atheos. Both are "semi POSIX"; that is, they don't intend POSIX compliance but do borrow strongly. The distinguishing feature here seems to be the non-X GUI and a file system that is reminiscent of Mac resource forks, but extended to multiple forks.
http://members.chello.nl/~w.cools/
This is one-man effort, and the source code is not available. It is surprisingly complete considering that, though there are of course major omissions still. I can't find anything you'd call unusual here: it's another OS.
This is a brash attempt to make an NT compatible Open Source operating system. As might be imagined, it's rather incomplete.
This is "mainly (99.9%) a one man project" according to the web page and looks to be more complete than Triangle. Again though, it's Just Another OS as far as I can tell.
The goal here is a free, 100% MSDOS compatible OS. Some people may wonder why, but in fact there is still a large amount of MSDOS code kicking about, some of it doing fairly important tasks, and porting it to other systems can be hard. As the day is fast approaching where you won't be able to buy real MSDOS at all, this could become very necessary.
http://os.inf.tu-dresden.de/drops/overview.html
The Dresden Real-Time Operating System Project uses L4Linux to run ordinary time-sharing applications alongside the real-time tasks.
This is for the Amiga lovers. For those who have never experienced the fervor of a true Amigo explaining why nothing since has even come close to what Amiga was, well, it's something everyone should experience at least once. Some of their rantings actually have a base in reality, so don't discount this out of hand.
http://aranym.sourceforge.net is for 32-bit Atari ST/TT/Falcon operating systems.
Another one person project.
I'm happy to add more if you'd like to point me at something you found interesting. ~
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A lot of Commodore 64's are still in use (several million, if you can believe one estimate). I guess that machine's OS could qualify for the list, eh?
--BigDumbDinosaur
Forth
Although it once held a bigger place in the world than it does today, I think Forth could be considered a Hobby Operating System. It was certainly my hobby (and livelyhood) for a long time.
-- Tom Zimmer (author of VicForth, 64Forth, ColorForth, F-PC, Win32Forth and others)
Got a web page to point at?
--TonyLawrence
The OS Projects page got literally dozens (if not hundreds) of these small OSes. Some of which quite interesting, but most just a stundents 100th try to create an OS.
http://www.osdev.org/cgi-bin/projects.cgi
Enjoy!
-- Michaela. [http://www.mausehaus.org?doc=ela]
Tue Mar 22 20:09:33 2005: 223 anonymous
http://www.osnews.com/story.php?news_id=10065 lists some other alternative OSes.
Tue Apr 11 20:35:29 2006: 1890 anonymous
while i am no longer doing Forth, I still have a home page, and it is located at; http://tomzimmer.blogspot.com in case anyone is interested,
Tom Zimmer
Author of zforth, FF, F-PC, Win32Forth, TCOM, ColorForth (for Radioshack Color Computer), VIC-FORTH (for Commodore VIC20), 64FORTH (for Commodore64)
Fri Dec 25 17:44:00 2009: 7825 TonyLawrence
So.. will ChromeOS be a "hobby" OS or carve a real space for itself?
Fri Dec 3 23:08:42 2010: 9146 anonymous
what about http://genode.org/. most interesting is http://genode.org/download/live-cds
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