Regarding a open posting list - what would be a possible migration scenario for a new list hosted at sourceware et al, given that we have an existing list with a number of subscribers?
vger is majordomo based. The current batman list is mailman. So i doubt there is direct export/import options for all account information. It should however to possible to simple export just the email addresses and import them.
sourceware uses ezmlm. So again, probably no direct export/import of everything, probably just a list of email addresses can be mass imported.
I don't know for sourceforge. All my googles turn up the project mailman which is hosted there, but its not clear if its what they use for lists.
Once the list is created, the MX record for lists.open-mesh.net needs changing to point to the new list server and the list server needs to be configured to accept emails for that domain. This is not difficult.
Probably the best bet is to pick a list server provider and talk to their sysadmins. I'm sure this is not the first time such an operation has happened.
Andrew