This is the default web interface displayed when accessing Pydio via a browser. It's HTML5 compliant and powered by the PrototypeJS library. The whole interface is built dynamically based on the various configurations gathered through all the application plugins.
The interface is themeable, you create new theme by duplicating the folders below res/themes/. Theming should be basically CSS tweaking. At the moment, "umbra" (latest) and "oxygen" (legacy) themes are bundled with the application, and you can change the theme by accessing the plugin options.
Although not necessary, at the moment the other gui plugins rely on this one to load all the core JS classes and bootstrap the Pydio framework in the client.