Teri Meri

The song "Teri Meri", from the soundtrack of this movie, is a version of a traditional Romanian Christmas carol whose name is "La Viflaim colo-n jos" (also known as "La Betleem colo-n jos").

You can find a comparison between them here:

http://www.youtube.com/watch?v=IVLb7kbLJ64

As this is a traditional song, I think there is no copyright to pay, and so I guess this version is not illegal. But it's ridiculous for Himesh Reshammiya to credit this song as if it were his original creation without mentioning the Romanian song.