Sorry for not keeping up with the "Athena on OS X" details.  Here's my experience (OS X 10.10.5, up to date patches from Apple) which might be helpful to some.

Athena from macports was working fine for me, but was many months old. This evening I did

  sudo port -v selfupdate
  sudo port install xorg-server

This installed many updates -- it had been awhile. I then did
  sudo port uninstall demeter
  sudo port install demeter

athena ran, but would not plot, in the way many had seen.  The gnuplot program was set to "gnuplot", but terminal was "qt".  Setting this to "wxt", plotting worked fine.

Not sure why that happened (I'm pretty sure it had been "wxt" previously), but it was easy to fix.   And I'm still very impressed that the macports solution works so well!

--Matt