I want to ask something :
Can J make Jnode with J2me or for embedded things and
can J make change in Jnode(kernel...)
Sorry for my English
PS:I waithing answers

Depends on architecture

The main question is, what architecture you want to run it on. If it's x86 you're perfectly fine. That basically involves making the plugin list smaller and removing some classpath stuff to make JNode and bootimage smaller.
If it is an other architecture (e.g. ARM/XScale) the work is much harder. At least you have to write a nanokernel (asm), a JIT and probably some drivers and modify some things in BootImageBuilder.

Best is, you tell us in detail about the architecture it is intended to run on, how much memory you have and what you exactly intend to do.

JNode stuff won't fit on a PDA easily

In my opinion JNode doesn't have a lot to offer yet to embedded devices. Like the JNode VM, J2ME is a VM that enables to run Java programs on a machine (a PC for JNode, a PDA or other device for J2ME). The stuff that JNode has that can run (slightly adapted) on another VM is the Commandline and the GUI. But both are not adapted for mobile devices.

I think if you go about adapting JNode stuff for something other than a PC, it's a whole different project. Could be an interesting one though!

Still, I can't imagine running desktop scale Java programs on a relatively slow machine like a PDA or a smart phone. Or the other way around.