In the United States Birkebeinerne is titled "The last King", and I was able to rent this on Amazon for US$3.99.
The film did an amazing job of depicting the story of the treachery surrounding the death of King Håkon Sverresson, and the flight of his infant son Håkon Håkonsson from assassination, with the two Birkebeinerne men: Torstein Skevla and Skjervald Skrukka.
The film was very well done and told without any Hollywood lunacy. It was an accurate depiction of 1206CE Norway. The costumes, props and effects were very well done. I was particularly impressed with the skiing sequences as they were obviously using period equipment and techniques.
There were also more than a few Forn Siđr references throughout the film, and they were fun to spot. I highly recommend this film.
Trailer at https://youtu.be/NosnWov78HM