Actually, Muslims don't have "their God", as opposoed to the Christians' God, and the Jewish God. To Muslims, it is all the same God - there is only one. They believe in the Torah and the New Testament and the Koran. They revere Moses and Jesus as major prophets. The only difference is that they believe Muhammad was the last prophet sent from God, the same God that sent Moses and Jesus. And from all the Muslims I know (which is lots and lots), they have no problem calling God "God". Allah is just Arabic for God.
I believe the "under God" portion of the pledge is just plain wrong. It clearly violates the separation of church and state that this country was supposedly founded on. But if you want ot go even further on this, one of my fellow co-workers was showing me some fancy certificate he got from the government upon his retirement in the Jag Corp., and it states, for the date, "In the year of our Lord, 2003". Give me a break!!