OpenProject is a web-based project management system for location-independent team collaboration. This free open-source application is released under the GNU (General Public License) Version 3 (GPLv3) and is available as a community edition and a chargeable Enterprise Edition. Development is mostly done by OpenProject GmbH.
It is very important to mention that this is a good/service that needs to be distinguished. Since they advertise paid plans on the website (https://www.openproject.org/pricing/), one might be inclined to think OpenProject is not trade-free. However it is possible to install the software on a server without trading anything for that. Therefore the source code with all of its functionalities is trade-free.
What is not trade-free is the basic/professional/premier/enterprise support, that one could opt in and would need to pay for. But the software itself is trade-free.