qdPM is a free web-based project management tool suitable for a small team working on multiple projects. It is fully configurable. You can easy manage Projects, Tasks and People. Customers interact using a TicketSystem that is integrated into Tasks.
Compatible with php 7.2+ and php 8.0+
DDesk is a ticket, task and issue management application. Profiled for desk-side support companies. Includes client UI, partner and internal UI. (Not in active development since 2006) Released under Apache License 2.0, user, reuse as you will.
Support Station is a ticket based customer support system. It is meant to be configurable enough to adapt to a variety of support needs and to co-exist easily with other systems such as subscriber based sites, online stores, etc.