|BeOS for Power Mac:
Yes. Although the standard BeOS install takes 130 megs of disk space (50MB of code and 80MB of VM scratch space), you can adjust the VM scratch space to a lower number to fit on a Zip. We don't recommend this for anything but trial use, but you can do it.
Since Jaz cartridges are 1GB, they should have no problem with the BeOS.
Of course, you have to be smart about using removable drives in this manner. After all, what happens when you eject the drive that has the VM swap file on it, and the BeOS needs to swap something to disk? Bad things, man, bad things.