If you are running OS X Tiger version 10.4.x, you will need to install X11 in order to use applications like OpenOffice and other Linux ports. It is located on the first disk of the installation DVD.

System/Installation/Packages/X11User.pkg

After inserting the installation DVD, make sure to scroll down to find the System folder. X11 can also be found when installing Tiger under the advanced option. There is an older version of X11 for previous versions of OS X that can be found on the web.