Doesn't look that difficult. I think all you have to do is to add this line to the file they mentioned in the instructions:

registry "{USER}" value "[user_folder]/Library/Preferences/Alias/maya/6.0/mentalray" end registry

... under this one:

registry "{MAYABASE}" value "/Applications/Alias/maya6.0/Maya.app/Contents/mentalray" end registry


And add this one:

MI_CUSTOM_SHADER_PATH = [user_folder]/Library/Preferences/Alias/maya/6.0/mentalray/include

in the section where the lines being with 'MI_CUSTOM_SHADER_PATH'



Rember to replace the 'user_folder' bits in the lines with the path to your actual user folder. If Mac OS is similair to Linux (which I read it is), your home folder should be like this: /home/your user name

Hope this helps...