Depends on your game model- and why would you need it on the client side if it's on the server as the server is doing the bulk of the critical stuff on it's side of things?Also, you DO need the physics to run a server. I'm not sure why anyone would think you don't. You still have to simulate the interactions in the world, which requires physics.
1) The bulk of the physics stuff is special effects, which is where the boost really needs to be- don't need that on the server.
2) Most of the games that I had the code to didn't manage anything other than a software event processing, model tracking, and rules enforcement bus system for the clients. The real load lifting wasn't ON the server. The server's a simple thing in many of the games that I've seen the code to.