We can use this forum (as described ) for communication.
Testing the email experience, and it is functional, provides threaded email. Also a little odd (markdown and including prior text look odd online, and if you make a message on the forum you do not receive an email).
I have gotten the source forge credentials from @ticheler and will be closing the soruceforge list promptly.
Any further messages sent to the email list will receive an auto-responder with an invite the join the Geonetwork developers - OSGeo Discourse group on discourse.