Clearview: I'm not sure if it says he is "jealous" in any other part of the bible, but part of their reason for changing the wording could have been to lessen the HUGE contradiction that is: Love does not get jealous, so if god is love, how can he be a jealous god? i think the way they worded it is an attempt to erase that contradiction, probably among other reasons.
Actually, 1 Corinthians 13:4 says love does not envy. I know we often use jealousy and envy interchangeably, but jealous generally suggests an offense to expected exclusivity (like a jealous husband, which God is described as to an unfaithful Israel going here, there and everywhere). Jealous implies at least some basis of a legitimate claim over the object of jealousy. Envy is malicious feeling from wanting what's not yours. (And a quick look at a lowly non-NWT translation--New King James Version--describes God as jealous or Israel driving God to jealousy in Deuteronomy 4:24 and 32:16, and Paul is jealous with a godly jealousy in 2 Corinthians 11:2...those are the examples from a very limited concordance).
So it seems like a paraphrase to say "exclusive devotion", but the words actually say His name is Jealous. Why is the "one true religion" pureeing the spiritual food? I'm with Mephis; I think it's about not wanting to confuse their claim to fame as the only ones using God's one and only name.