Is unpainted drywall with mud/joint compound dangerous to be around?
At best, breathing drywall or drywall compound (mud) dust can irritate your respiratory system and is best avoided.  One problem is that it is very fine and if you sand it much, you need to use special masks that can filter the fine particles, plus you don't want to use a regular vacuum to clean it up - I believe it will clog the filters.  This mainly concerns people who work with it regularly, and a small amount is normally not anything to worry about unless it causes physical respiratory symptoms.  Some people are more susceptible to this, like asthma sufferers.

I would want to at least paint the walls and joints with primer paint as soon as possible.  I'm surprised if that has not been done.