1. Download the khmer Unicode fonts (http://www.khmeros.info/drupal/?q=en/download/fonts)
2. Add the Khmer Unicode keyboard (system preferences-international-input menu)
3. Install X11 (a graphical unix interface) – this comes with OSX Tiger on the set-up disk. If they have an earlier OSX system, they can download it off the Apple website (but it’s 41MB) You run X11 by going to applications-utilities-X11 and need to have it running it before you install openoffice
4. Install OpenOffice (downloadable from their website – 130MB!!!)
5. Install “fondue” if you want other non-ttf fonts besides the system fonts that come with open office (http://fondu.sourceforge.net/)
6. Otherwise you can skip 4 and just copy the KhmerOS fonts to the openoffice font folder (ctrl-click on open office – show package contents – contents – openoffice.org2.0 – share – fonts)
7. Now it should work!
Special thanks to David Narita for these instructions!