So far, OpenOffice.org 3.0 for Mac has been limited to Intel machines only. However, plenty of Mac users are still running PPC machines and would like to use the latest OOo on their computers as well.
Current versions available for download are developer builds, so you may encounter lots of bugs. And new versions may be released superseding those linked here. Try this page and look for the latest directory to see if newer builds are available. (As of this writing, the most recent is “Dev_DEV300_m36“).