Flyspray is an uncomplicated, web-based bug tracking system written in PHP for assisting with software development. It was originally conceived when the Psi Jabber client project couldn't find a bugtracker that suited their needs, and has been made available for everyone to use for their own projects.

Flyspray is Free Software, released under the GNU Lesser General Public Licence Version 2.1. This essentially means that you can get Flyspray and use it free of charge. The source code is available, and you are welcome to modify it to suit your needs. Submitting your changes back to us is entirely optional, but we'd love to hear from you!

Features include:

• Web-based, platform-independent
• Multiple database support, currently MySQL and PGSQL
• Easy installation
• Easy to use
• Multiple projects
• 'Watching' tasks, with notification of changes (email or Jabber)
• Comprehensive task history
• File attachments
• CSS themes
• Advanced search features (though easy to use)
• Atom/RSS feeds
• Two syntax options for task descriptions and more (Dokuwiki / plain text)
• Voting for tasks
• Dependency graphs

more on http://flyspray.org/about