Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
jtrac - JTrac is an open source and highly customizable issue-tracking web-application written in Java.
Bots UI Kit - Fully customizable Sketch UI Kit for Messenger Platform
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.
Landing UI Kit - Handcrafted UI components for landing pages
Bugify - Bugify is a simple PHP issue tracker, designed to offer powerful bug tracking capabilities in an easy to use system.