Papyros: platform independent parallel processing

Papyros, written by George Sakkis, appears to be a fairly simple way to use surplus cycles on other machines. Written in Python, it is platform independent using a master-slave model. Remote communication is handled by Pyro. To parallelize your program, some code changes are necessary, but they appear to be minimal. Each slave platform needs to have a Python app running to receive the processing requests, but other than that, all "wierdness" happens on the master.
    http://code.google.com/p/papyros/wiki/README

I don't see any special security provisions so it's fair to assume all players must be mutually trusted. YMMV.