Trac - Trac is a project management and bug/issue tracking system. Provides an interface to Subversion and an integrated wiki.
Bugify - Bugify is a simple PHP issue tracker, designed to offer powerful bug tracking capabilities in an easy to use system.
Pivotal Tracker - Pivotal Tracker: The awesome, lightweight, agile project management tool for software teams. Get your 30-day Free Trial started today!
16bugs - 16bugs is an all-in-one bug tracking software that makes it easier for you to manage all sorts of bugs in performance with the simple interface; ultimately, you will be more productive for sure.
Gitea - A painless self-hosted Git service
Traq - Traq is a PHP powered project manager and issue tracker featuring multiple projects, milestones...