Why? I just subscribed to all messages and use it as any other mailing list – in my email.
UPDATE: wow, didn't know you can't even read messages without being google-user. Yeah, that's boorish a bit.
UPDATE2: turned out that's not true. You can read google group perfectly fine without signing in: https://groups.google.com/forum/#!forum/tmux-users
http://groups.google.com/group/%(groupname)s/boxsubscribe?email=%(email)s
[1] https://github.com/bsandrow/google-group-join