Scarab is meant to be a highly customizable, full-featured bug tracker, offering more or less the union of the features offered by other bug trackers: data entry, queries, reports, notifications to interested parties, collaborative accumulation of comments, and dependency tracking.
It is customizable through administrative web pages. You can have multiple "modules" (projects) active in a single Scarab installation. Within a given module, you can create new issue types (defects, enhancements, tasks, support requests, etc.), and add arbitrary attributes, to tune the tracker to your project's specific requirements.
As of late 2004, Scarab was getting close to its 1.0 release.