@fr0der1c the legacy version is the one currently in production and being used.
So it is still being updated to support the and fix the bugs that come along while organizing the events.
the open-event-server version however is the one which is under development and once it becomes production ready and also the frontend webapp is production ready then we will completely migrate to that and stop using the legacy code.
So though it is really helpful sometimes to solve the bugs that appear in legacy code since it is under production but at the same time the idea is to speed up the work of the current development so that it can be made production ready quickly and be used in place of the legacy code.
So I personally would recommend that you start contributing to the open-event-server project. But I would be happy if you would contribute to legacy as well