In our restaurant we have the microwaves in the open where you can be behind it while it's on. Usually in normal houses you don't see the back, only the front. Is it safe to be behind it while it's on? I know it sounds like a dumb question, but I heard someone say once that it wasn't safe, because of radiation or something. just wanna be safe.
A home grade (or dual use unit), unless defective beyond reason (eg if there is a hole in it or an interlock is broken) will be always safe from all directions, since any risk of harming persons or animals and/or creating radio interference (Microwave ovens share a frequency band with WiFI!) behind a wall or in the room below or above is unacceptable.
Same can be expected to apply to a commercial unit, unless it would be some very special device not intended to be used as a normal microwave oven (eg one meant to be operated on a conveyor), which can be expected to come with very clear warnings attached in that case.
Yes, microwaves are safe, no matter which side you're on. There's probably a warning label on your microwaves, and you can double-check to ease your mind about any other possibilities; I imagine it will say things like not to take it apart and not to immerse it in water, but it is safe when used normally.