- [OTOBO](https://otobo.io/en/) - Flexible web-based ticketing system used for customer service, help desk, IT service management. ([Demo](https://otobo.io/en/service-management-plattform/otobo-demo/), [Source Code](https://github.com/RotherOSS/otobo)) `GPL-3.0``Perl/Docker`
- [Roundup Issue Tracker](https://www.roundup-tracker.org/) - A simple-to-use and -install issue-tracking system with command-line, web, REST, XML-RPC, and e-mail interfaces. Designed with flexibility in mind - not just another bug tracker. ([Source Code](https://www.roundup-tracker.org/code.html)) `MIT/ZPL-2.0``Python/Docker`
- [Trudesk](https://trudesk.io/) - Trudesk is an open-source help desk/ticketing solution. ([Source Code](https://github.com/polonel/trudesk)) `Apache-2.0``Nodejs/Docker`
- [Zammad](https://zammad.org/) - Easy to use but powerful open-source support and ticketing system. ([Source Code](https://github.com/zammad/zammad)) `AGPL-3.0``Ruby/deb`