Borallus is a Colonial outpost.
When considering the Fleet's next stop, after their exodus from the Twelve Colonies, Sire Uri proposes that Borallus should be their place of resupply. According to Uri, whose argument is that Carillon is too far away, "everything we need is there".
Unfortunately, being a logical place to resupply, Adama states that a Cylon task force would undoubtedly be waiting for them there (Saga of a Star World).