The joke about Emacs being an operating system is an old one but lately the idea seems to be being taken more seriously. Here’s the latest example. Significantly, the poster, Bi-Jean, is a self-confessed n00b who doesn’t work in the tech industry, just someone who likes playing with computers and is curious about the best ways of using them. The idea seems natural to Bi-Jean.
If you believe, as I do, that the best way of thinking of Emacs is as a latter-day Lisp Machine, the idea of it being an OS makes more sense. Specialized applications aside, there’s basically no function that you can’t implement from within Emacs except arguably a decent Web browser. From that perspective, the “real” OS is viewed as a set of device drivers for Emacs. It’s a point of view adopted by many Emacsers who claim not to care what OS it’s running on.
My own view, as someone who does almost everything from within Emacs, is that “My operating system is Emacs and Linux/macOS/Windows is just a set of device drivers” is a nice joke that captures an underlying truth but isn’t truly realistic. I always say that I do virtually everything in Emacs and Safari but the “virtually” provides a little wiggle room. For example, I use Fantastical to sync my calendar across all my devices, the Reminders app to set a reminder across all my devices, and the Apple Messages app for texting—although I do use Emacs to compose the text—so it’s not really Emacs all the way down.
Still, a case can be made that in an essential way, Emacs really is my OS. Perhaps more important is the fact that it doesn’t really matter. I do most of my work—other than browsing—from within Emacs and if that makes Emacs my operating system, fine but I also depend on macOS for more than just running Emacs.