The current version of the bulletsim physics engine will start on the latest release version of opensim, but there is a memory leak that will manifest itself pretty fast if you have more than 1 sim. for the xmir grid with 30 sims, it eats memory at a rate of 5 Mb/sec which will run the software out of meory in about 30 minutes.
The main developer of the bulletsim code is working on a fix that should sort out the issue, but for now ODE physics is what you must stick to. Of course this also means it is not possible to run VAR regions with opensim on OS X.