BugKick is an open source bug tracking and task management application (source is hosted on GitHub) that is “light” in means of features (which i sometimes nice).
It is built with PHP-MySQL and allows teams to define projects, add tasks to them (which can be tagged with anything like “bug” or “feature request”) and assign to teammates.
Discussions under each task is possible, status updates about each of them are delivered via e-mail and closed ones are not deleted but kept.
There is an API for integrating it into our own apps and a JavaScript snippet + a contact form helps users to submit bugs too.
Requirements: PHP, MySQLWebsite: https://bugkick.com/
Download: https://github.com/aaronmusopen/bugkick
Download: https://github.com/aaronmusopen/bugkick