I found the song online here, which came with a nice montage video of the first season or so of the History Channel's Vikings. (The preference for selecting battle scenes as well as the almost complete absence of women strike me as interesting, if somewhat ambiguous, indicators of the video's intended audience.)

So first it's worth noting just how very little we know about Viking Age music. In fact, we know next to nothing. Our evidence consists of: (1) contemporary instruments found in other parts of northern Europe, particularly in Anglo-Saxon graves, (2) later descriptions of music in Norse poetry and prose, mostly written about 400-500 years after the events covered in the first few seasons of Vikings, and (3) the meter and rhythm of the later Norse poetry, some of which is considered to be scraps of poetry actually composed during the Viking Age or even earlier. As you might imagine, these scraps of evidence provide only slim evidence for how actual musical performances would have been staged and experienced during the Viking Age, although we get some indicators.

For example, poetry is based on alliteration rather than rhyme or meter (like pop songs or Shakespearean sonnets), which suggests that (a) there was no regular rhythm, and (b) the 'down beat' was more important than the 'back beat'. It's hard to imagine what this would have sounded like for most modern listeners. Pop music usually emphasizes the back beat—this is usually where the cymbals crash or the audience claps in most rock and roll. A heavy down beat is more closely associated with traditional music like marches and some folk tunes like Irish jigs, as well as most techno and house, although these are all decidedly very rhythmic styles that would not easily accommodate Norse poetry, which was organized around having the right number of alliterating words but could have a fair bit of variation in the actual length of the overall lines. Jigs and techno are both similar in that the modern listener can easily count regular measures of two or four, even if they don't understand the faster rhythmic or melodic figures happening within those measures. Viking Age music would have been ... somehow ... different.

The Helvegan recording, of course, seems to use some type of poetry derived from styles of poetry attributed to the Viking Age. I'd recommend checking over at /r/Norse if you'd like to know how accurate this is. There's also a driving beat, which is good and fun for the modern listener, but again, it doesn't fit our best guess about Viking Age music based solely on the information we can derive from Viking Age lyrics (which could be shaped to fit a driving beat but weren't composed to emphasize it).

The Helvegan recording also uses a modern scale (do-re-mi-fa-sol-la-ti-do) oriented in a minor key (emphasizing a different set of notes in the scale than a major key; minor la-me-do vs. major do-me-sol). The modern scale is in fact very modern, dating only as far back as classical music and wholly inappropriate for music written in the Renaissance or earlier (i.e. less than 500 years ago). The pitch of a note (A B C D ..., do re me fa ...) is actually just a way of describing its wavelengths, or the frequency at which those wavelengths hit our ears. In different times, people preferred different sets of pitches. Our modern Western scale ultimately derives from some ideals about the proportions between the pitches first proposed by Greek mathematicians and philosophers, which were later adjusted through trial and error to increase their constructive interference (which we sense as harmony). So the modern scale is actually a unique combination of physics and cultural preference, and it's highly unlikely that Viking Age Scandinavians or their cousins living abroad either east or west had a similar set of pitches. (Our knowledge about how pitches have changed in recent times derives from empirical observations about how organs have been made with pipes of different lengths, which are a clear measure of wavelengths; Greek philosophers were able to describe wavelengths without clearly knowing how sound waves worked because they could still talk about the length of strings on zithers and lyres, which are an adequate proxy for the sound waves that the strings produce.)

So in sum, I'd say that the Helvegan recording takes some of our very limited knowledge of Viking Age music (primarily the lyrics) and fills in the gaps with modern musical practices and preferences (the rhythm, scale, and even the instrumentation). It's hard to do this well, and I'd actually rank this recording high alongside some other good works I've heard, such as the album Vittrad by Garmarna (1994). If you're looking for something which is even more closely informed by our admittedly sparse knowledge of Viking Age music, I'd strongly recommend Edda by Sequentia (1996) and Sturlunga Saga by Voces Thules (2009). These groups both produce music heavily informed by academic study on premodern music while performing at concert-hall standards. Check them out!