The AWB does not apply to pump shotguns only semi-auto. So a pump can have pistol grip, +5 shots, folding stock, bayonet lug, detachable mags, anything and everything.
Only issue with this gun, is if it is an AOW "Any Other Weapon". An AOW can not be shouldered so in other words a shoulder stock can not be added. It is a way to make short AR's or shotguns, but it must be done with a "virgin" receiver, one that never had a shoulder stock on it before. And once it is designated an AOW it has to stay that way.
Judging by the length of the gun (looks over 26" already), I would say it is not an AOW, but all you need to do is ask Mossberg. I can not remember since I am not a Mossberg expert, and I have yet to buy or own an AOW myself.
What is stamped on the gun?
Here is a good example of an AOW shotgun. In my state we can NOT own short barreled shotguns, but we CAN own an AOW