[NYer]

For a bishop to greet someone in the name of Allah is heresy

Actually, 'Allah' is the Arabic word for God. There are several Eastern Catholic Churches where the Gospel is read in both English and Arabic. Using the word 'Allah' in reference to God, is not heresy.

[Old_Mil]

Actually, 'Allah' is the Arabic word for God.

Nope. From a historical perspective, Allah is what amounts to a contraction of the phrase Al Illah, refering to "THE [moon] god", supreme diety of the pre-Islamic Arabs. Sort of their version of Zeus, if you will.

Even if you accept a modern Muslim's conception of Allah as a monotheistic being instead of chief of a polytheistic religion, the character of the diety circumscribed by the term "Allah" and the term "Jehovah" are radically different.