We all need to keep in mind that John's audience is in high school. They aren't going to be enraptured if someone makes them listen to a recital of Beowulf in Anglo Saxon or Old Norse, they aren't into it the way John is and certainly not the way some of us are.

The whole thing is an erroneous stew if you want to look at it from a purist's stand point. The movie is, in far too many ways, dreadful. Beowulf is not Viking but pre-Viking. However it's just a starting point, if John builds from it without being overly picky on one hand and not too factually sloppy on the other there's always the possibility that he can spark someone's interest in WMA or archeology or whatever.