WHAT ABOUT WORDPRESS IS NODE.JS?
Node.js is used to built almost all front-end tooling. Calypso is built with popular node tools like WebPack, Babel, Jade, Uglify, Hot Loader, Marked and over 100 other modules. WordPress start using node.js, because its one space a lot of people using these tools.
ISN’T IT JUST FOR WORDPRESS.COM ACCOUNTS? WHAT ABOUT SELF HOSTED? PLUGINS? CUSTOM POST TYPES?
Calypso is an editor and an RSS reader for WordPress.com sites. You can, however, use it to manage your self-hosted WordPress account. Once you enable Automattic’s JetPack plugin, you can manage your content with Calypso.
Now, you can only manage, Pages, Posts, Themes, Menus, Plugins and a few settings. Everything you need to manage a blog.
What is missing is an interface for custom fields, custom post types and any custom interface that a plugin would expose. This is a deal killer for most devs as not using WordPress just as a blog.