OTRS

= "OTRS comprises the leading Open Source Help Desk Software OTRS Free and several free features for ITSM, Surveys, Time Accounting, Systemmonitoring as well as the the OTRS iPhone App".

URL = https://www.otrs.com/download-open-source-help-desk-software-otrs-free/

OTRS is licensed under the Affero General Public License V3 (AGPL) that ensures you can download, install, use, and modify the software at no cost.