Red Hat's directory server

Red Hat's directory server

While I can see where you're coming from, I think there are a few other important points there:
(a) GPL with exceptions is still way better than proprietary. It's still free. AFAIK you can also take it and "pure-GPL" it if you feel the need.
(b) The modules don't have to be non-free, and the exception doesn't have to permit non-free modules. It can simply be for modules that, for some reason, must have additional restrictions. A good example is MySQL, which offers exceptions for PHP and (AFAIK) OpenSSL.