First, radiocarbon dating comes with error bars. The date range identified is from 570 C.E. to 632 C.E. Given that Muhammad is thought to have founded Islam in the period from 610 C.E. to 630 C.E., and that date keeping was relatively good in this period, this would seem to confirm rather than dispute the traditional accounts.
Second, the radiocarbon dating was performed on the parchment only, not the ink, as the article belatedly notes. Given the practice of ancient scribes to re-use parchment repeatedly, a rather unfortunate practice that has resulted in the loss of uncountable ancient texts, the age of the writing would be controlling, not the age of the parchment.
Third, I'm forced to draw a rather unfortunate conclusion from this information. The assertion in this article seems deliberately calculated to undermine the historicity of Islam. There is a very sad and shortsighted movement in some corners of military scholarship right now that identifies Islam itself as the enemy, often beginning with Huntington's "clash of civilizations" narrative and ending with some examples of sheer lunacy, such as the recent article by a West Point associate professor arguing that legal human rights scholars are "an Islamist fifth column."
Islam is one of the world's great religions, and like all religions it inspires everything from massive works of charity to zealotry, persecution, and bigotry. I have known many good people who drew their strength from Islam, and condemning an entire religion is a type of insanity that is directly contrary to the founding principles of the United States.
Islam is not the enemy. Those who would pervert it for their own violent ends are. We cannot lose that distinction.