it's not dangerous at all, plenty of RWD cars have an open diff.
however, if you drive like a twit and disregard the way your car handles (open diffs are less predictable sometimes) then you will come to grief.
remember that VLSDs are speed sensitive diffs, the only differential action is due to viscous goo - there is no actual contact so you will be able to spin the wheels in opposite directions even on a healthy diff.