I think, that the 133/266 MHz ARM XScale CPU is to slow and the 32 MB memory is not enouht to ran SETI.
Am I right, that the NSLU2 is fanless ? - I think it is a big risk for the device, because the higher CPU util results in more heat. - Not shure, if CPU throtteling will gave any benefit to prevent overheating, but with a slow CPU and CPU throtteling you have to pay attention to met the deadline.