Having received a copy of the album Havnarkórið 45 ár as an extraordinarly generous gift, I can confirm it does indeed exist as a physical 2-CD set, published by Tutl in the Faroe Islands (www.tutl.com). However, I cannot actually find evidence of it on their website. Maybe my Google skills are deserting me.
The Holmboe works occupy all of the first disc, not almost all as I previously said. It turns out there is another Faroese folksong arrangement not mentioned in the catalogue I work from, called Rura, rura barnið. Without knowing Faroese, but with some knowledge of related languages, my guess is that this is a lullaby.
That makes three folksong arrangements, together with Sigmunds kvæði (I am now changing how I write this to match the album) and Ólavur Riddararós.
The rest of what I said about the Holmboe compositions on the disc appears to have been accurate. The second disc contains works by a variety of composers, with the most contributions from Hans Jacob Højgaard and Knut Olsen.