You can stream on older machines. I use an old C2D Mac that should be running 10.6 in terms of "power", and I can still stream with a little finagling.
You may have some luck using CamTwist + Flash Media Live Encoder; searching for the two of them together should pop up some tutorials. That's what I used back on 10.6. I also -think- older builds of CocoaSplit might work on your OS, but I'm not sure. Good luck.