I have found the solution. The issue is with the caffe that came with openpose. It’s no good. You should install your own. In fact I found it in the documentation. Here’s the link (look under Mac OSX Version header)and here it is for quick reference:

Also as a side note, if the default installation fails (i.e., the one explained above), install Caffe separately and set BUILD_CAFFE to false in the CMake config. Steps:

Re-create the build folder: rm -rf build; mkdir build; cd build.
brew uninstall caffe to remove the version of Caffe previously installed via cmake.
brew install caffe to install Caffe separately.
Run cmake-gui and make the following adjustments to the cmake config:
BUILD_CAFFE set to false.
Caffe_INCLUDE_DIRS set to /usr/local/include/caffe.
Caffe_LIBS set to /usr/local/lib/libcaffe.dylib.
Run Configure and Generate from CMake GUI.