The FreeBSD-based macOS clones: airyxOS & helloSystem

Two open source operating systems that mimic the look and feel of Mac OS... both built on FreeBSD.

Mac OS has long had an association with BSD (and FreeBSD)… dating all the way back to the NeXTSTEP and OpenStep roots of Mac OS X, which included quite a few userland tools from BSD.

Note: Yes, I know that Apple has re-branded their system to be “macOS” instead of “Mac OS”. But I’m oldschool. And I think “macOS” looks stupid. So I’ll be ignoring their rebranding in this article. I’m a cranky old man who yells at clouds, that’s just how I roll.

So, perhaps, it is only natural that, when someone is looking to create a clone of the modern Mac OS… they look to FreeBSD as the base system.

As it so happens, there are two such systems under active development: airyxOS and helloSystem.

airyxOS

The team behind airyxOS doesn’t hide their goal of cloning Mac OS. Not for a second.

“We love macOS, but we’re not a fan of the ever-closing hardware and ecosystem. So we created airyxOS — an OS aimed to provide the finesse of macOS with the freedom of FreeBSD.”

In fact, the top two promoted features of airyxOS are, specifically, the look and feel of current Mac OS systems.

But, to be completely fair to airyxOS, their feature set goes way, way beyond the look of the system.

For example, the developers have focused on recreating the folder structure of Mac OS and — perhaps even bigger — providing some level of Cocoa API compatibility (which is the defacto development framework on Mac OS).

All of which is both impressive and ambitious.

helloSystem

The other primary “Mac OS Clone” out there is helloSystem.

HelloSystem is the brainchild of Simon Peter, the man who created AppImage (.iso files that contain a Linux executable, along with the bulk of necessary libraries… thus making “drag and drop” software installation possible on Linux systems).

The purpose of helloSystem is described thusly:

“For mere mortals. Welcoming to switchers from macOS. Not just a theme. Not a clone of anything, but something with which the long-time Mac user should feel instantly comfortable. The latest technologies, without the complexities of Linux distributions. Without lockdown. Without Big Brother. The user in full control.

Less, but better!”

Calling helloSystem a “clone” of Mac OS really isn’t accurate. It is more… inspired by Mac OS. It feels to me to be a love letter to some of the better parts of both modern Mac OS X… as well as the classic Mac OS.

In truth, helloSystem is quite excellent. If I were to pick a FreeBSD to use right now, it would most likely be this one. The amount of love and attention that have gone into the details of the system — combined with Simon Peter’s excellent track record of producing stable, long-lasting technology — make it most appealing.

The two have much in common

If you look through the feature sets of both airyxOS and helloSystem, you’ll fine many commonalities (other than both of them deciding to make the first letter in their name lower case).

In fact… at one point airyxOS was a direct fork of helloSystem. From the airyxOS FAQ:

We are in fact working with helloSystem! As some people have noticed, Airyx 0.2.X was basically helloSystem. (That was the second PoC. The first had been built on vanilla FreeBSD and had no GUI at all.) Under the hood, however, Airyx 0.2.2 has a partial implementation of Cocoa, a modified compiler & linker that support frameworks, and several other additions that make it distinct. We have similar philosophies, and share technology and cooperate where it makes sense (e.g. Filer), but the project goals are quite different.

helloSystem wants to create a computer that is simple to use, open, elegant, small and fast. Older MacOS X and Classic are an inspiration to what that might look like, but they are not explicitly trying to create an open-source Mac. In fact they're mostly avoiding Objective C and XML plists and other Mac technology in favor of simpler and/or more modern ways (e.g. Qt, C++, JSON).

Airyx is explicitly trying to be compatible with Mac software at a source and eventually a binary level, without losing support for FreeBSD/X11 software, and to implement a very similar experience on the desktop and at the command line. For example, on Airyx you can type open -a MyApp image.jpg and have image.jpg open in MyApp. You will find things in (mostly) the same directories as a Mac, like ~/Library or /System/Library/Fonts. Airyx is not as concerned about keeping the OS as small and simple as possible, and more concerned about making it clean, secure, performant, and compatible - implementing many of the features I use daily in macOS while skipping the lock-in and "tabletization" of the computer.

There are other “Mac Clones”

Neither of these represent the first attempts at recreating the look and feel of MacOS on an open source operating system.

Some Linux distributions have made a name for themselves almost entirely by copying the look and feel of Mac OS. And other systems have attempted to tackle API compatibility with the modern Mac — such as MidnightBSD and GNUstep.

GNUstep with a semi-modern Mac theme

… but none have been as polished or advanced as either airyxOS or helloSystem.

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