The current list of ET members on http://einsteintoolkit.org/members.html is out of date (mostly I guess because there is no way to update one's information).
Eg looking at http://einsteintoolkit.org/members.html Charalampos Markakis would be at Southampton (he has been at NCSA since 2016), Philipp Moesta would be at Caltech (he has been in Berkeley for a couple years now). Tanja Bode is no longer at Tuebingen but at UCSC etc etc.
My suggestion would be to contact all persons listed for their current institution and remove those that do not respond within a month. For future registration I suggest that we ask for an email address and ping the addresses once a year, removing stale ones. We should also include a paragraph to contact firstname.lastname@example.org to update ones affiliation in any email send out along with the registration.