The author is definitely right in saying that Emacs is an OS, because it runs "programs" that interact with a common datasource. The issue is that those "programs" are not the ones of your baremetal host. The sequel that makes sense would be a text editor that allows host programs to be run seamlessly on the text. Once again the geniuses behind Plan 9 have shown how novel their system was by creating acme ( https://w…
Just like Emacs is a poor imitation of the developer experience on Lisp Machines, ACME is a poor imitation of developer experience on Oberon and Mesa/Cedar.