In way of Australians who use STP, there are about 5 of us.
I don't envy you being stuck in Brisbane, you should head North.
Free travel is very possible In Australia.
Hitching is Illegal in QLD, it comes under a law called begging arms, which is not an arrestable offense, or technically even a fineable offense, generally the police won't even bother pulling you up about it. but if they do, all they will do is tell you to get off the road and they'll run an ID check on you hoping that they can find something against you. The worst That has happened to any one I know while hitching in QLD is the police making them buy a bus ticket..
in the rest of Australia it is Illegal to be a pedestrian on the freeway, but this law isn't really enforced and walking 20 meters back to the on-ramp will make it legal.
squatting is possible. the only place with harsh enforceable laws on squatting is the NT. but since they brought the law in during early 2010, nobody that I know of has been caught.
there are plenty of empty houses around, if your in Brisbane try looking around coorpooroo and the other areas where they are building the new bus malls. I had a squat there in 09 that lasted for 7mnths before we left.
nothing that I know of in the way of communes, but all of the (long running) forest blockades are essentially communes with a more active focal point. and so are the Info shops, (Brisbane doesn't have any) are similar and both are very open to and mostly comprised of travelers.
apart from that. Dumpsters are amazing, busking brilliant, train hopping and hitching yachts is also easy and commonplace.
I hope some of this helps..