damiancugley wonders if every website in the world secretly wants to be Twitter.
If anything the problem is too many backup programs
The aforementioned ljArchive program is windows-only. Turns out one you start looking there is an infinity of LiveJournal archiving programs.
After some Googling I found ljdump, which is Python-powered and therefore runs happily on my Mac. Its author is working on a program to publish the resulting heap of XML files, ljpublish.