Thanks! Space on SD-card or CF-card is a lot cheaper than in former times. I'll try to extract the dev-image on a desktop linux with squashfs-support (e.g. with Slax or Puppy LiveCD) and transfer the files on a SD card for the Zaurus.
That is a great idea, & here's one better: Repack the uncompressed image files in cramfs format, which is supported by default at least in Sharp's C860 ROM. Developer Image version 1.5 was provided in cramfs format, though that package has long since disappeared from the Internet.
Done.
You don't need a special Linux with squashfs support. BTW. often squashfs support in modern linux is squashfs 4.0 and that can not mount squashfs 2 which is the version of the dev-image 1.6.
For most linux distros there is a package squashfs-tools with unsquashfs, a tool to extract squashfs archives. And this tool can extract squashfs version 2 too. unsquashfs (or modern 7-zip which can also extract squashfs) is available for Windows too, but i didn't try these because i was afraid that symlinks in the dev-image will get broken.
After extraction you can make a cramfs archive with mkcramfs from the cramfsprogs package.