I just uploaded a new VC plugin to github that allows linking vc rooms for systems where no direct api access is granted. It offers the option to only show the link to registered users as well.
Additionally it can get the VC redirect URL via an external mapping service.
One question: I was able to show the join buttons in the contribution list and meeting style timetables, but not in the conference timetable. Would that be something of interest? And if yes, any hints how to add such a feature