mantis -- A web-based bugtracking system
http://mantisbt.sourceforge.net/
Mantis is a web-based bugtracking system. It is in active development and is considered beta. It is written in the PHP scripting language and requires the MySQL database and a webserver. Mantis has been installed on Windows, MacOS, OS/2, and a variety of Unix operating systems. Any web browser should be able to function as a client. It is released under the terms of the GNU General Public License (GPL).