As I have said on the IRC channel, I'm waiting to get my hands on a mac. Once done, I will try to check if the second option can be used.
apart from possible name clashes, it also make more difficult to openxcom. For example i have to add the following to get it built with makefile
CXXFLAGS=-I/usr/local/include/yaml-cpp make
or autotools:
YAML_CFLAGS=-I/usr/local/include/yaml-cpp ./configure