Regular reminder that wordpress.com is a different software product to wordpress.org :)
wordpress.com runs their (relatively) newer JavaScript-based stack; wordpress.org (which is what we're talking about here, unless I misread the article referenced here completely) is the LAMP stack version.
It's written in JavaScript; it runs on node.js - at least the front-end part of it (https://github.com/Automattic/wp-calypso). I don't know what is running on the backend but I don't think it's LAMP?
The point I was making though is that "WordPress" can mean two different things - wordpress.org (the self-hosted LAMP version) or wordpress.com, which is a SaaS offering (so the language is more or less irrelevant unless you're really interested in running your own admin frontend, I guess).
Calypso is our JS dashboard that lets you manage all your sites in one place, plus get cool WP.com features like stats and notifications. It's just a REST API client, just like the iOS and Android apps.