It is still a mono system. An OS is really not care you run c, lisp, VM and another os fundamentally. In this sense emacs is not an OS. And is mono. Just like

It is still a mono system. An OS is really not care you run c, lisp, VM and another os fundamentally. In this sense emacs is not an OS. And is mono. Just like Common Lisp. An internal “closed” system can have diversity. But not put external as first object, just as OS would not normally running OS task as the most important thing but running user land task. A “closed system” like emacs and Common Lisp is unlike say OS and vs code, they are not the kind that you as the user program of the emacs or Common Lisp can be of a totally different idea of how in addition to what and still co-exist nicely. Can you write a program of c and run under and with emacs and Common Lisp ... Even Api and extension need to be purposed for external interaction as it needs to assume difference that with a totally different approach. Totalitarian can say harmony with difference but in real it is just totalitarian. Democracy can be suppressed but ultimately is a diverse system.