yep as everyone said, has to be secured. my mate got pulled over by the hoon squad. the booked him for a few things (like bov and cutting the front bar), and after they had gone over the car he asked them what exactly the law was on pods in qld. the cop said as long as it is secure its fine.
on a side note, i used to be on the magna forum, and some guys on there were putting chicken wire under the motor to catch the pod if it fell off. now i've run a pod on a few of the cars i've owned, and i've never even had one come loose, let alone all the way off.