- [Bugzilla](https://www.bugzilla.org/) - General-purpose bugtracker and testing tool originally developed and used by the Mozilla project. `MPL-2.0``Perl`
- [django-todo](http://django-todo.org/) - Pluggable, multi-user, multi-group, multi-list todo and ticketing system - a reusable app designed to be dropped into any existing Django project. ([Source Code](https://github.com/shacker/django-todo)) `BSD-3-Clause``Python/Django`
- [Erxes](https://erxes.io/install/) - Marketing, sales, and customer service platform designed to help businesses attract more engaged customers. ([Demo](https://demo.erxes.io/), [Source Code](https://github.com/erxes/erxes)) `GPL-3.0``Javascript`
- [FreeScout](https://github.com/freescout-helpdesk/freescout) - Open source clone of Help Scout: email-based customer support application, help desk and shared mailbox. `AGPL-3.0``PHP`