It seems access to any part of the repository is now forbidden:
$ svn ls https://svn.macports.org/repository/macports
svn: E170013: Unable to connect to a repository at URL 'https://svn.macports.org/repository/macports'
svn: E175013: Access to '/repository/macports' forbidden
This affects all developers. And unfortunately, due to the recent rsync server problems, the only workaround available was to tell users to switch their MacPorts installations to use the svn server instead of the rsync server, so now those users will also experience errors yet again.
Keith said all of the Mac OS Forge infrastructure was rebooted, so perhaps this is related.