Miroslav Volf has an interesting article on whether Allah is the same as God. In some places, apparently, it matters a lot:
Under the influence of Malay militants, in 2007 the Malaysian Home Ministry decided to enforce the 1986 law prohibiting use of the word 'Allah' in non-Muslim publications. The Malay-language edition of the Catholic weekly Herald was forbidden to use 'Allah' to denote the God Christians worship. In a parallel move, in 2009 the government also ordered customs officials to seize some 15,000 Bibles because they used 'Allah' as a translation for 'God'.
The Herald filed a suit, and at the beginning of 2010 Judge Lau Bee Lan of Malaysia’s High Court overturned the government ban. She ruled that 'Allah' is not exclusive to Muslims. In response, angry mobs attacked churches, often with firebombs. The government itself was displeased by Judge Lan’s decision, and it appealed the ruling…
If Christians were to use “Allah” to designate their own god, Muslims would be 'confused.'
Malaysia’s Appeals court has now ruled that 'Allah' may not be used to designate the God of Christians, thereby upholding the original 1986 prohibition.
Volf then describes the views of some Christians who agree. According to R. Albert Mohler, the President of The Southern Baptist Theological Seminary,
From its very starting point Islam denies what Christianity takes as its central truth claim - the fact that Jesus Christ is the only begotten Son of the Father. If Allah has no Son by definition, Allah is not the God who revealed himself in the Son. How then can the use of Allah by Christians lead to anything but confusion … and worse?
'Allah' is simply Arabic for 'God,' just as 'Theos' is Greek for 'God' … A slightly different way to make the same point is this: 'Allah', like 'God', is not a proper name but a descriptive term. 'Barack Obama' is a proper name; 'the president' is a descriptive term… For the most part, we don’t translate proper names; 'Obama' is 'Obama' (transliterated) in all languages. We translate descriptive terms; 'the president' is 'predsjednik' in Croatian. 'God' is 'Allah' in Arabic and 'Allah' is 'God' in English.
He then makes a rather different point:
Even more important than the meaning and the character of the word 'Allah' is the millennia-long practice of Christians: ‘Arabic Christians and Arabic-speaking Jews since long before the time of Muhammad have used the name 'Allah' to refer to God … Thus all Arabic Christian Bible translations of John 3:16 say, 'For Allah so loved the world …' Up to this day, all Arabic Christians use 'Allah' for God.
So far, I’m pretty confident that Volf is right and that the people who want to distinguish the two must have ulterior motives for doing so. I’ve often had discussions with evangelical Christians who insist that Allah is different from God, and in every case there was a strong desire to reject all Islam as totally erroneous, if not devil-inspired. To them it was important to insist that when Muslims worshipped Allah they were not worshipping the God of Christianity. Either Muslims were worshipping a non-existent being or they were worshipping an evil demon. These Christians were bothered about this point as a theoretical principle; the ones I spoke to had not troubled themselves to ask Muslims what they were actually doing.
I would want to add an additional point. The people who insist that Allah is not God are thinking like polytheists, a position which neither Christianity nor Islam approves of.
Let’s ask what happens in divine cyberspace. Somebody prays to Allah. What happens to the prayer?
Option One: The one and only God receives the prayer. It gets into God’s ‘inbox’. God then rejects it because it was addressed to Allah. This implies that there is a rule about how to address prayers. Using the term ‘Allah’ disqualifies it as a valid prayer, perhaps a bit like failing to add ‘through Jesus Christ our Lord’ at the end. Either this rule is God’s creation, in which case God has a petty prejudice against people who speak Arabic, or we’re in the realm of magic.
Option Two: Because the prayer used the word ‘Allah’ it never got as far as God’s inbox. It got lost in divine cyberspace because Allah does not exist. In that case what Arabic-speakers need to do is submit a question to the Heavenly Support Forum. Who is in control of the system for directing prayers to the right destination? If there is only one God, the answer must be God. So we’re back with Option One, with a God who arbitrarily chooses not to hear the prayers of Arabic-speakers.
Option Three: Because the prayer was directed to ‘Allah’, it went to the inbox of the divine being who has the domain name ‘Allah’. In other words there are two gods, the Christian God and a different one called Allah. But this is real polytheism, which Christianity and Islam both reject.
If God does not accept prayers directed to Allah, either God has an arbitrary prejudice against Arabic-speakers or there are two different gods. In either case both Christianity and Islam are wrong about God.