When following the wbcd.org instructions, you need the original Sharp-ROM. You can only restore it with a NAND-backup (which could result in the device becoming unusable, but I haven't had any problems with this yet). Then following the instructions (which are a bit confusing sometimes, and one 'next page'-link is referring to the same page) you get the OS converted to (mostly) English. Installing the applications should work on any ROM, but they probably won't have japanese font/input, so they're pretty useless. (I tried to install japanese support on Cacko one time, but it didn't work perfectly (or as perfectly as in the Sharp ROM), so I gave that up.)
The biojapan site seems to be mostly about the older Zauruses without Linux, but the info about dictionaries seems to be interesting.
