Phabricator is a collection of open source web applications that help software companies build better software.
Effective June 1, 2021: Phabricator is no longer actively maintained.https://admin.phacility.com/phame/post/view/11/phacility_is_winding_down_operations/
Tuleap is the first fully libre and open source software (GPL licence) for Enterprise Application Lifecycle Management. Tuleap is provided by the Enalean company and the community members.
Tuleap vs Polarion opinions
Powerful tracking system, high configuration, intuitive and easy to use agile and requirements management.
Cradle by 3SL is a requirements management and software / systems engineering tool for agile and phase-based projects including MBSE, agile development, document & project management. Cradle supports small or large teams, either co-located or distributed.