Also, 2.6.0-test6/7 and I believe recent FreeBSD kernels already have
  the required realm patches. I still have to update the patches for
  2.4.22/23 and will at some point submit them to Marcello for inclusion.

Hm, a version without an OS name.  Probably GNU/Linux....

But seriously: NetBSD-current has realms support and it works fine.

For the NetBSD 1.6 branch, apply the patch at
  http://www.ir.bbn.com/~gdt/coda/coda-realms-16-u

This was done by Phil Nelson, and I've been running it for quite a
while without problems (due to the kernel; I don't claim venus never
gives me trouble!).

-- 
        Greg Troxel <gdt_at_ir.bbn.com>