Atlassian Open Sources its User Interface (AUI) – Developer Documentation

The Atlassian User Interface (AUI) is a set of reusable, cross-browser tested, high-quality JavaScript and CSS UI components. We developed AUI for use in Atlassian applications such as JIRA, Confluence and others. As a plugin developer, you will find AUI useful to provide standard, sophisticated UI components that plugin into the host application’s user interface. Refer to the version matrix to see which AUI version is included in each host application.
(Link: Atlassian Open Sources its User Interface (AUI) – Developer Documentation)