URL: http://www.bugzilla.org
License: Open Source (MPL)
Language: Perl
Requirements: Perl, CGI capable web server, MySQL, Sendmail 1)
Recommended: Apache with mod_perl
Bugzilla is the “Defect Tracking System” or “Bug-Tracking System” created by Netscape and spun off as open source as part of the Mozilla organization. It began as a series of perl CGI scripts, but has grown quite sophisticated. Not only does it handle the Mozilla bug database, but hundreds of other companies and organizations use it as well.
Bugzilla has quite a few dependencies. There is a checksetup.pl script included with bugzilla that will help you find dependencies and you'll need to brave CPAN (or PPM)
There are two main versions of Bugzilla in use. The 2.x series is the traditional one and is stable, if less than beautiful. Bugzilla 3.0 is still fairly new, but has some nice features, including an improved appearance and web service API.
Redhat has a very nice AJAX UI for their bugzilla.
Bugzilla is a supported option on QA Site. I am working on a new Bugzilla UI and on integrating it with the QA Site dashboard. We also have a Bugzilla sidebar and may create a Firefox extension.