The most recent X2Go client mostly works with MacOS.  There is a problem however, it only works if you use sh, ksh, bash, or some other Bourne shell derivative here.  If you use csh, tcsh, or other non Bourne shell derived shell it will fail to map the keyboard correctly.  This is because it uses bash (and apparently only the /bin/sh subset of commands) to execute xmodmap to do keyboard mapping.  It only does this on MacOS, and consequently this only is a problem if you are originating from a Mac OS/X based machine.