Flyspray Bug Tracking
Flyspray is an uncomplicated, web-based bug tracking system for assisting with software development. Whereas Trac has ubiquitous WikiFormatting and a focus on integration, FlySpray is a dedicated bug tracking system.
FlySpray is written in PHP and shares many similarities with Trac's ticket system, in particular the way a ticket or task is displayed. They have some advanced features compared to Trac, like ticket dependencies (see #31 and the TracCrossReferences), multi-project support, tracking ticket progress (#2217 and #1084), etc.
Flyspray's development stalled in 2013, but restarted in 2015 with the promise to deliver version 1.0 in April-June 2015.