I don't remember what determinism is in computer science. I meant that if you set up a physical scenario with ODE, and let it run twice, you'll get two different outcomes. A box that falls on its corner near a ledge might topple off the ledge on one run, and then on the next run, tip back and settle on the ledge. Like this guy says: http://gamecreator.blogspot.com/2007/03/ode-determinism.html
Box2D does appear to be worth trying, so I'll move on to that and keep my Phys2D exploration on hold for now. I know of JBox2D, and I would prefer to use that since it's pure Java--but maybe Java bindings to Box2D itself would also be worthwhile. I don't immediately see any of those around though.