Kinda dumb question, would it possible to create atom editor and all the core packages typed by myself?
I mean, without forking the repo
Not sure what you mean. You mean, by
npm installing all packages and by some public API put everything together?
If so, not really. But there are lots of “core things” on Atom that are just packages - you could, in theory, re-create then, but it’s no easy task…