On Hackernews there was once a skeptic of postmodernism who got into a debate with a Derrida fan. The skeptic said "If deconstruction is not BS, how about you explain to us, in plain English, what it's all about." The Derrida fan replied "No. How about
you demonstrate that you've read Husserl, Heidegger, Hegel, Nietzsche, Freud, and Levinas.
Then we can begin to talk about Derrida."
If Alan Kay were like the Derrida fan, then he could have rebuffed anyone who came asking what the Dynabook was about with "How about you demonstrate that you've studied the achievements of McLuhan, Montessori, Papert, Minsky, Engelbart, etc. Then we'll talk." Of course he's not like that so he's going to try to give the reporter a bit of the background he has in those things and let them figure it out for themself.
The Dynabook is supposed to be, roughly, an iPad with a keyboard, stylus, and a Lisp Machine-like OS. Of course Apple and third parties have closed the gap with keyboards and styli but it's the OS that's the really important bit because in order for a Dynabook to be a Dynabook it must not be a thing that you can just download and run preapproved apps on. You have to be able to discover -- and change -- the entire system from the bare metal on up. Think "Stallmanism on steroids".
It's like a television you can talk back to. Computing is a dynamic medium that demands interaction from its user, so to deny the user the ability to question and change the assumptions of the medium is to lock them in to certain stereotyped modes of interaction and deny the full richness of the medium. This is where Kay's "real guitar vs. Guitar Hero" analogy comes in. You can either have a device that offers its full potential up front, like a real guitar, or you can have a device that can only be used in circumscribed ways, in vague imitation of having the full richness of the original device, like Guitar Hero. The price you pay for having a real guitar, or a real Dynabook, is what we call "ease of use" -- the ability for a complete neophyte to pick it up and immediately display something resembling proficiency with it. (It is much easier for a trained data-entry clerk to operate a 3270 terminal than it is for that same clerk to fill out a modern Web form, but that sort of ease doesn't count.) And Apple has really doubled down on ease of use, at the expense of everything else wonderful about having a powerful computing device you can hold in one hand. To the point where it's become just like regular, can't-talk-back-to-it television.