If memory serves me right, Ryan Greene wrote:

>   anychance this could / will be ported to a sparc64 arch?

m0n0wall runs atop FreeBSD 4.9, which doesn't support the sparc64
architecture.  (FreeBSD 5.X does, although support for various machines
of the sparc64 architecture varies.)

I've not heard of anyone working on such a thing, nor of any plans.

The components making up m0n0wall are pretty architecture-independent
and all open-source, so you could probably roll your own version if you 
are so motivated.

Bruce.