What is GNOME OS?

With the release of GNOME 3.38.0, we started producing and distributing bootable VM images for debugging and testing features before they hit any distribution repository. We called the images GNOME OS. The name itself is not new, and what it stands for has not changed dramatically since it was introduced, but let’s restate its goals.
GNOME OS aims to better facilitate development of GNOME by providing a working system for development, design, and user testing purposes.
The main feature of GNOME OS is that we can produce a new system image for each commit made in any of our modules. The ability to have these VM images is truly amazing since we are dealing with hundreds of modules that depend and integrate with each other, and with the lower layers of the OS stack. This effort represents a game changer with regards to being able to automate the boot and session initialization, testing design and implementation changes, catching regressions earlier in the development cycle, and many other possibilities.
GNOME OS will also allow the engagement team to more easily create visual assets ahead of the release, present features and raise bug fixes with the free and open source software community at large, and make initiatives like the release video a lot simpler. Journalists will be able to get their hands on the new release of GNOME before the final release. 

What GNOME OS is not

Despite the its name, GNOME OS should not be regarded as GNOME’s own platform or general purpose operating system. As much as I would personally like for it to be, and have talked in the past about it, we have to recognize that it’s not, and for good reasons. In its current state, GNOME OS is still an incomplete reference system. It’s the closest approximation that we have to a GNOME platform OS, but we don’t actually have the resources that would be required to support a fully realized, general purpose OS for everyday use.
Maintaining an OS would, at the bare minimum, require keeping up with security fixes (CVEs), doing hardware enablement, and having some kind of user support story. Each one of these is a gigantic task requiring a dedicated team to do properly, and GNOME is not currently set up to be able to tackle them. Distributions put a lot of effort into building their platforms to maintain the changes coming from various upstreams and QAing them together.
Furthermore, many GNOME contributors are already working for companies that develop distributions (Canonical, Red Hat, SUSE, Endless, etc.) and it’s unclear how many would be willing or able to maintain another one.

Who is it for?

Firstly it’s for designers, so they no longer have to suffer through countless hours of trying to build software themselves, in order to test the latest development versions of some of our core modules (most notably GNOME Shell). Tightening that feedback loop is incredibly valuable for delivering a polished product. After that, it’s for the release team, so it can validate releases before slinging them out the door; for developers and translators, so they can have a complete system to test and debug their changes on; for our downstream distributors and OS vendors, so that they can have a known to be working baseline against which they can compare their own products. Last but not least, it’s for the machines and robots that keep an eye out for regressions.