Cool idea. The program on the zaurus seems like it runs well. But the map downloader will only download maps of Japan. Were you able to get it to work?
zroadmap so far might be a better gps sollution even though it is a few years old.
I'm using it in japan, and zroadmap is US-only
I've used pgmap on a debian zaurus, qgmap on a sharprom zaurus, and both on a debian laptop
you can download maps with pgmap on the desktop and rsync them to the zaurus for qgmap as the map dir is compatible
if you edit pgmap's DownImgs.pm and change hl=ja to hl=en you can get maps with english text
if you edit pgmap's pgmap.pl and change
if ($map->{backup} && !$map->{selected} ) {
to
if (!$map->{selected}) {
then you can shift-A anywhere to select all tiles on screen even without a backing map at the wider zoom level (works ok at level 14 but dies sometimes at 15 or 16, though you should be able to find the area you want ok at 14)
it would be nice if it was modified properly to provide a world keymap at the widest zoom as a starting point...