It's not possible with DR at the moment, but is possible via Backburner. There is a request filed to make it possible. Do note that even if working, or if using Backburner in the meantime, you will need to have Render Node licenses for the other machines (or if using just one machine to render, you'll have to accept that your main machine can't render while the other one is rendering... which I guess it couldn't anyway, because the DR results would still be taking up the VFB on the main machine :) )