Im not an NFL guy but I i think players are allowed to wear equipment from any manufacturer they choose as long as that brand name is covered/removed. This is a stipulation created by "official NFL" companies like Riddell.
Im pretty sure Riddell supplies helmets to the NFL teams for free in order to be labeled "The official helmet of the NFL". The trade off is no other helmet manufacturer name can be displayed.
I have heard the NFL mandates that every team has to have a certain percentage of players wearing Riddell helmets in order to not violate the contract with Riddell.

If any of this is not correct, someone please update me. AND, looking at that pic, I would think there would be a fine for that Shutt neck pad not being covered.