For a briefer introduction, Calypso is an editor and RSS reader for WordPress websites. However, with enabling Automattic’s JetPack Plugin, one can use Calypso for managing the content.
While WordPress is using PHP since 2000, the company’s chief and Founder Matt Mullenweg consider the interface a struggle despite its bug fixes. Calypso, on the other hand, comes with open libraries such as Node and React to enable more social, stats, likes and notifications in the code.
This means that the open sourcing would enable more external development, more plug-ins, custom interfaces and distributions on and around WordPress.com. While it offers plug-ins to manage a blog, there is a missing interface for custom fields needed for the websites.