Found this on the Burning Man website:
"Gifting food or fresh juices to the public, requires a permit from the Nevada State Health Division. Any kitchen serving 125 or more persons at a time, whether public OR private, requires a health permit. Go to http://health.nv.gov/BFHS_EHS.htm
, and scroll down to the flame icon for specific "Temporary Food Information for Burning Man". You don't need a permit for bar ice, but your ice must come from a commercial source approved by the Health Division, like local stores or our own ice sales."
Doesn't exactly answer the question if a permit is required for a bar, but if you aren't serving fresh juice I don't think you need one. We never get one.