The general aim is to make a fully featured skin that emphasises both content and editing tools, with multiple view modes for showing everything, focusing only on content (winter), or switching to dark/night viewing. One day it will actually do this.
This skin is being used on one or more Wikimedia projects. This probably means that the skin is stable and works well enough to be used by such high-traffic websites. Look for this skin's name in Wikimedia's CommonSettings.php and InitialiseSettings.php configuration files to see where it's installed. A full list of the skins installed on a particular wiki can be seen on the wiki's Special:Version page.