The jobs are being submitted through the Create Backburner Job... dialog in Maya. We're using Macs, though not command line (although Maya generates a CmdJob command when it submits). I know what you mean by putting the process in the background, but I'm not sure that applies in this situation. The backburner manager is sending out tasks through its own internal logic to available render machines. I don't want a render machine to be working on multiple tasks at once, however it would be nice for the manager to send out tasks from multiple jobs, if that makes sense.