This is the first time I have heard of this web site. So I checked their study Bible, and they have switched to calling Christ "the Messiah". While Jesus of Nazareth was indeed the Messiah/King of Israel, He is far more than that after His resurrection. He is called "the Lord Jesus Christ" in the New Testament, and in the New Testament the Greek word is "Christos", which translates to "Christ".
Personally I get a little annoyed with this change, since the world has know of Christ as "Christ" for over 2,000 years. It just sounds a little cute. And since the majority of Jews rejected Christ as their "Messiah" it seems a little strange that Christians keep reverting to "the Messiah". When Christ comes the second time, He will NOT comes as the Messiah, but as "King of kings and Lord of lords" (Rev 19:16). However, the Antichrist will present himself as the false messiah of Israel in the near future.