I added some instruction to the ATF internals/scripting bit of the wiki for installing liso. Since it needs gnuplot and this requires all kinds of other stuff it seemed like a good plan to document it for future generations.
In short the message is simple. If you're using a mac then you should install X-code from your OSX dvd and then install MacPorts. Your life will be greatly enriched and future dealings with all things linux will be nicer.