While there are no absolute definitive answers here – everyone's use case is different, after all – we've discovered ten distinct examples that fall outside the usual bounds.
Our list even includes a few true outsiders, independent operating systems built from the ground up which serve mainly to prove just how difficult it is to create an entire functioning OS without a large number of brains working on it.
Everything here can be tested reasonably within a virtual machine, so if something grabs your interest don't hesitate to download and give it a try.
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ArcaOS is an operating system based on the last IBM release for OS/2. While OS/2 barely survives as a legacy system, even after being extended for a while as eComStation, ArcaOS is still being actively developed with Spanish and German language editions currently under beta testing and scheduled to be released in the next update.
ArcaOS includes a robust Unix compatibility subsystem, featuring a variety of ported Linux apps and some drivers, but still features the OS/2 Workplace Shell.
ArcaOS is a 32-bit OS that runs on the x86 processor architecture, so should be compatible with some particularly old PCs. Though its native file system is JFS, it ships with drivers for the FAT32 file system.
There are two editions available: Personal, which retails for $129 per license, and Commercial, which retails at $229 per license, though volume discounts are available. The personal edition includes 6-months support and maintenance, while the commercial edition includes one-year of priority support and maintenance.
We're a bit sad that BeOS didn't take off. A stylish multitasking OS that introduced a whole host of features that Windows, Linux and macOS would later adopt for their own, BeOS was a true multimedia innovator that left the market with a whimper when its rights were sold to Palm in 2001.
The spirit of the closed source BeOS lives on in the form of Haiku, an open source re-implementation which began development immediately after Be's demise, and it has been in development since.
Built from the ground up but designed to be backward-compatible with its classic quarry, Haiku follows BeOS' lead in its entirely modular design, allowing different components of the OS to be developed concurrently. It’s been a while since the OS had a stable release. In fact, even the second beta release of its under-development branch was released almost two years after the previous one.
It's worth playing with just for the cleanness of its desktop, and there are working web browsers and media players, although it's still rather experimental and many of the features of BeOS haven't quite been fully realized as yet.
- You can download Haiku here
Linux, as you may know, is a ground-up reinterpretation of UNIX. ReactOS does the same for the Windows NT architecture upon which all modern Windows versions are based. It's completely open source, uses no proprietary Windows code, yet ReactOS is designed to be (and in some cases actually is) compatible with Windows drivers and applications.
Your mileage may vary – it's certainly not going to play nice with high-end games or software, and ReactOS isn't quite up to the Windows 10 level yet. It's currently aiming at full compatibility with Windows Server 2003.
So it's clearly a bit behind the times, but ReactOS does have its uses. Incorporating parts of noted Windows emulator Wine, it runs LibreOffice, Firefox, Opera and more quite happily, and can even manage some earlier versions of popular commercial applications like Adobe Photoshop. Furthermore, ReactOS now natively supports more file systems than all Windows versions combined.
Given that it's free, it's certainly worth a test to see if any of your older business-critical applications are compatible – setting up workstations without Windows licensing is a tempting prospect, although we can't vouch for its resistance to attacks.
- You can download ReactOS here
A ridiculous amount of business software relies on MS-DOS, even to this day. We're still seeing bespoke, newly-developed text-mode apps that run directly from the shell, probably because the complexity and potential for disaster that graphical interfaces add to the mix is not worth the risk in situations that demand 100% uptime.
That business-critical software may rely on MS-DOS, but it’ll run just as happily on a FreeDOS shell. As its name suggests, FreeDOS is a fully-compatible but completely free and open source remake of DOS that can handle just about everything its proprietary counterpart can. That does, of course, mean no multitasking, no protected mode, no GUI, but it'll run your games and can even manage Windows 3.1 as long as you're running it in standard mode.
As you might expect, it's not a static recreation of the final commercial DOS release in 1995, and indeed hasn't been static since it first emerged in 1998. In fact, FreeDOS remains in active development, and features a number of integrated improvements compared to its rather archaic ancestor.
- You can download FreeDOS here
Wayne OS comes from a Korean startup that forked the open source Chromium OS (from which Google derives its Chrome OS) to create an OS for regular 64-bit machines instead of Chromebooks.
Originally called Chromic OS, the project changed its name to Wayne OS in 2019. Instead of a traditional installation, the distro is designed to be installed in bootable USB flash drives.
Wayne OS is available in two versions -- Free and Paid. The Free version is meant for all kinds of end-users. To install it, simply download its compressed installer and then extract the executable installer from the archive and fire it up. This will bring up the Wayne OS installer.
Select the version you want to install and then point the installer to the USB disk you want to install it on. Wait for the installer to download and copy the necessary files to the USB disk. When it’s done you can unplug the now bootable USB disk and use it to run Wayne OS on any 64-bit computer.
- You can download Wayne OS here
While Linux is a recreation of UNIX, FreeBSD is more of a continuation. It was initially developed by students working with a Research Unix source license obtained by the University of California Berkeley – the 'BSD' bit stands for Berkeley Software Distribution. The only reason it's not called BSD Unix is because of the pesky trademark and licensing gremlin.
The OS runs on its own kernel, and all of its key components have been developed as part of a single whole. Linux, on the other hand, is just the kernel; the rest of it is supplied by third parties so it lacks BSD's overall coherency.
While FreeBSD is a highly complete and very reliable operating system, it doesn't come with a graphical user interface by default. This is where FuryBSD steps in. It delivers a much more usable FreeBSD using a combination of a familiar graphical desktop environment with some additional tools and functionalities.
The latest release is based on FreeBSD 12.1 and packs in the latest quarterly packages from the FreeBSD repository. The OS is available with two desktop environments in separate ISO images. There’s one based on Xfce 4.14 that’ll perform well on under-equipped machines, while the other with KDE Plasma 5.17 is meant for well-stocked computers.
- You can download FuryBSD here
Sun Microsystems' SunOS – which evolved into the rechristened Solaris – began as a proprietary UNIX distribution designed to support Sun's SPARC processors. Its list of supported hardware widened as it grew, and in 2005 Sun released the source code in the form of OpenSolaris, leading to advanced community development. And then Oracle purchased Sun, renamed the OS once more to Oracle Solaris, and decided to cease source releases, effectively closing the source once again.
Sometime after this move, the community took it upon themselves to maintain OpenSolaris. They decided to ditch its development tools and processes and created the OpenIndiana Hipster branch to modernize the OS. Hipster is compiled with GCC instead of Sun Studio and follows a rolling release model and the release team puts out installable snapshots every six-months.
What makes OpenIndiana (OI) approachable to new users is that it runs familiar apps on its desktop. It uses the Mate desktop along with its cache of tools as well as a handful of mainstream productivity apps such as Firefox, Thunderbird and Pidgin. While there is not much to write home about OI’s default cache of apps, one that caught our eye was the TimeSlider app for taking incremental ZFS file system snapshots. It isn’t enabled by default, but is fairly intuitive to setup and use.
- You can download OpenIndiana here
KolibriOS is written in the FASM assembly language and based on the source code of the MenuetOS operating system. It boots in a flash and gives you access to a number of useful apps. There’s no installation involved, though you’ll have to make sure you select the option to save the changes you made during the session when you shut it down.
The OS supports FAT and NTFS file systems and ships with drivers for popular audio, video and Ethernet hardware. The desktop is fairly intuitive to operate, and new users aren’t reprimanded for casually exploring the desktop and its various apps.
The only shortcoming of the OS is that its productivity apps aren’t really mature enough for everyday use, and the lack of a package manager doesn’t help its case either. On the other hand, if you like retro gaming there’s no better OS.
- You can download KolibriOS here.
The goal of the OS is to create a fully functional OS for Computer Science students and alternate OS enthusiasts like us. Considering the fact that it’s primarily an educational system, Visopsys surprised us with its usability.
The OS boots in a snap and gives you the option to either launch the installer or boot into a Live session. The inclusion of a very capable partitioner in the installer is another pleasant surprise.
The desktop is fairly simple to navigate and includes a handful of essential apps, plus handy administration and configuration utilities. But attempts to use it for regular desktop tasks won’t take you very far, as the OS is missing a web browser and there’s no package management to help you pull in additional apps and utilities.
Visopsys does a nice job of masquerading as a regular desktop, but it really is a very capable CS project and should be treated as such.
- You can download Visopsys here.
Nostalgic open source fans can still get their dose of Amiga-esque goodness through Icaros. This is a distribution of Aros, which is an OS based on the AmigaOS API. It’s important to note that this isn’t a clone of AmigaOS, but an implementation of its API in a new operating system. Unless you’re familiar with the AmigaOS of yore, you’ll have a pretty tough time getting to grips with Icaros.
It’s tricky to install, and it’d be a frustrating experience to even attempt to explore the OS without first reading its user guide. First-time users should appreciate the fact that the OS is distributed as an installable live CD to whet their appetite. Click on the eye icon in the panel to get an Applications menu, or on the filing cabinet to get a selection of manuals.
Icaros has pretty decent hardware support, but still don’t expect it to work with fancy graphics cards and all wireless network hardware. Icaros has all the apps you need to use it as a regular desktop, but its real specialty is retro gaming, and that’s one area in which it really shines.
- You can download Icarus Desktop here.
Gone but not forgotten: other Operating Systems
It's worth noting that there have been a number of other operating systems that were previously popular but have since been discontinued. One of the most famous of which is AmigaOS, used in Amiga personal computers during the 1990's and which had a reputation for solid stability.
However, here are a few more that you may or may not have come across before now.
OS/2 may not have set the world on fire, but it actually maintained a decent industrial and commercial install base long after its desktop aspirations died. eComStation was a derivative OS that uses classic OS/2 technologies on modern hardware.
Much like its ancestor it's been developed with security and stability in mind for commercial applications. We see the claim 'zero downtime' repeated all over the place, and while it's theoretically possible to lock up your hardware with the wrong application, this is something that could have been a real killer feature.
There's a host of open source software ported to eComStation including Firefox, OpenOffice, VLC and more, and it's capable of running DOS, Java and OS/2 applications. You almost certainly don't need it, but if there's something system-critical and OS/2-only that your business relies on, running this on bare metal is a much more reliable idea than setting up a VM.
As eComStation hasn't been updated for some years, if you're looking for OS/2 support and development it might be best to look at ArcaOS in the above list.
12. Syllable Desktop
Developed between 1994 and 2001, AtheOS – initially planned as a clone of AmigaOS but later following its own path – was the work of a lone Norwegian programmer, Kurt Skauen. After Skauen abandoned the project, its GPL-licensed source code was picked up by the community and Syllable Desktop was born.
The majority of it is composed of unique code, although certain components have been pulled from the vast library of open source Linux programs; there's also a Server version, which is more traditionally Linux.
Syllable's key selling point – ignoring the fact that it's free – is its speed and lightness. The creators recommend a Pentium CPU with 32MB of RAM, which should give you an idea of how lightweight it is. Slap this on a modern PC and you'll likely never have seen an OS so quick.
Syllable does lack the ports that make other indie operating systems attractive, though it contains a number of native apps for web browsing, email, VNC and more. We're not entirely positive that it's still active – the last official update was some time in 2012 – but if there's a very, very old PC you need to resurrect with reasonably modern system architecture, try this.
The development of SkyOS has sadly been halted, but it's still worth looking at as an example of an OS constructed from scratch. Developed initially as an open source project by coder Robert Szeleney, SkyOS was based on concepts gleaned from other platforms but didn't originally borrow their code.
That said, a few components are based on other packages – there's no sense, for example, developing an entirely new compiler when GCC already exists, and the SkyFS filesystem is forked from OpenBFS. Later in its life, Szeleney appears to have experimented with a version of SkyOS built on top of a Linux kernel in an attempt to help with driver compatibility.
The source was closed midway through its life, and Szeleney continued development based on feedback from a popular (paid) public beta program. Unfortunately the struggle to keep up with ever-diversifying computing standards became too much for the lone coder, and development was halted in 2009, with the most recent beta made publicly available in 2013.
It's obviously incomplete, and not suitable for any kind of business environment, but as a curio to run within a VM it's very interesting.
Whether the extreme religious doctrine behind it interests you or not, TempleOS is an interesting example of a completely independent, unique OS. It's been made and maintained with extreme dedication by one man, Terry A. Davis, over the course of ten years.
TempleOS – programmed entirely using Davis' own language, the excellently named HolyC, which you also use to interact with its shell – deliberately includes no networking and absolutely no hardware support beyond that which forms the core PC system. So what's the point?
TempleOS has been built from the ground up with what seems like no hang-ups on existing operating systems. The entire thing is hyperlinked, meaning you can quickly burrow down to the source of a program just as easily as you can find its dependencies, and it's super-quick; there's no paging, so the whole OS gets up and running within a second or two.
It's unlikely you'll be able to use TempleOS for anything solid, and Davis' well-documented mental health struggles haven't helped its standing in the community. But it includes a huge number of interesting ideas, particularly the blurring of the division between document and program, which could impact more traditional operating systems. Which is why, despite TempleOS’s development having ceased with Terry’s passing in 2018, the OS is still available for the curious lot out there.
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