Hmm -- it looks as if OS X 10.2.4 supports journaling, and not just on the Server edition. There's no "enable journal" button in the Info pane of Disk Utility, but when I opened a terminal window and typed:

sudo /usr/sbin/diskutil enableJournal /

... It created a journal file and enabled journaling on my new Powerbook G4.

(See this AppleCare article for details.)

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