I am not a Norse native, but I have a deep interest in Norse culture and viking ages. So, when I read the runestone after spawning as a faerie, I was enchanted by it. I had only heard of the Hávamál but never actually researched it. So, naturally, I was going to research this sentence. I translated it myself, with help of a Swedish friend I play with. The translation seemed wrong so I tried translating it from Icelandic instead of Swedish, and I came up with the correct translation.
Granted, I thought fé was a fae at first, but after looking closer I recognised it as 'vee' which is Dutch for cattle, and since our historical ties I figured this must be a remnant of those ties. So, I recognised it as cattle.
I then searched the sentence on google (I had left the spawn by then, and I didn't recall the Nordic sentence, so I googled the translation) and came up with the full proverb. It's part of the Gestaþáttr or in other words, the laws on how to treat visitors. Besides some rules on how to treat others it also gives some advices on how to deal with being a visitor (for instance, always spy around when you enter a house because you never know if your enemy is sitting there.. practical advice for HnH too? Maybe.)
I discovered quickly that a part of the saying/rule is left out.
Deyr fé, deyja frændr, deyr sjálfr et sama; this is all in the runestone.
Ek veit einn, at aldri deyr, dómr um dauðan hvern. This was left out by Jorb and Loftar. Perhaps it's coincidence but this translates to 'I know one thing that never dies, the judgment of a dead man's life. I am assuming it's coincidence because it didn't fit on the stone, but it's pretty eerie considering it's.. striking relation to HnH. I found it oddly fitting that this was left out, after all, judgement of a dead man's life often gets forgotten in this game. Perhaps not by the Gods, but by other players surely it does.
To celebrate my favorite era, the Viking era, and to celebrate that a saying of the Vikings made it into the game, I made my own runestone for my small community that I am playing in.

Bare is the back of the brotherless man. It's made to remember that without eachother we are nothing but barebacked hermits. (Not that there's anything wrong with hermits

If you want to read more about the Hávamál and the laws and examples given by Óðinn I suggest you start by reading https://en.wikipedia.org/wiki/H%C3%A1va ... l#Contents It's wikipedia so it lacks many details but it's as extensive as you'll get it without paying for a book or anything of the sort.
Thanks Jorb and Loftar for including this, it really made my day after I figured out what it was. Hail Óðinn!