If you wish to discuss the complexities of Greek grammar, then we will; but, suffice it to say (and I’m sure you won’t, no traditionalist ever is), the two accusatives in Philippians 2:6 (*harpagmon *(robbery) {accusative singular masculine noun} and *isa *(equality) {accusative plural neuter adjective}) comprise an example of the object-complement construction.
What this means is this: An *object-complement double accusative *is a construction in which one accusative (in this case, *isa *(equality)) is the direct object of the verb and the other accusative (either noun, adjective, participle, or infinitive) (in this case, *harpagmon *(robbery)) complements the object in that it predicates something about it. Because the object-complement construction shows up in the New Testament in various arrangements, word order is by no means an accurate criterion by which to distinguish the direct object from the complement in Greek.
That last sentence is important. In a case like the verse at hand when neither of the accusatives is a proper name or pronoun, the presence of the article (to {accusative singular neuter}) is required in order to indicate which accusative is functioning as the object of the sentence.
Or, in short, the NJB translation is correct and any hints of Arianism are present in the Greek, not just the translation; however, this doesn’t necessarily have to be the case. Rather, what we see here is that although the Father and Son are one in their essence (that is, both of them existing in the form of God), they are distinct in their persons (that is, they each respectively fulfill certain roles and functions that are peculiar to their own Person. The Father sends the Son into the world and the Son does not try to abdicate his role by grasping for functional equality with the Father, but, on the contrary, the Son obeys the Father.