This never seems to go that smoothly, despite the best efforts of the NCL people. The problem is that the GCC on Homebrew has now moved on from GCC4.8 against which the NCAR-NCL graphics were built.
It all works well provided that the gcc dylibs are in /usr/local/lib, so if you download the gcc/gfortran binaries as the installation suggests you need to
sudo ln-s /opt/local/lib/libgomp.1.dylib /usr/local/lib/libgomp.1.dylib
and the same for libgcc_s.1.dylib and libstdc++.6.dylib, then
All should be well.
NB Currently, the ncl-ncarg package on ubuntu 14.04.1 is missing PlotCharData and gives a bunch of errors.