Maybe, I was talking to Hróða about it because in theory I didn't think there'd be anything wrong with the Norðmenn against the Englisc. It would be easier of course, if we use the faction names as they are in-game.
Meh, leave them be. Not everybody that loves this mod wants to know how these archaic languages worked, many just want to play as a warrior clad in period gear and have a nice melee along with our across the board gameplay improvements.
Which is totally fine and acceptable, because in the end that's what Vikingr really is. You have a right to care for the languages and many people appreciate advice regarding it, but don't be snobs about it either.
I thought of contributing to Vikingr a spangen helmet, but I have been having problem after problem with it. OpenBRF deleted some of the faces to my imported helmet, and when I used back-facing faces, the lighting is all screwed up.
I'm still happy my first 3D model came out like this.
There are books about it, even courses at universities and possibly other institutions.
With a decent linguistic knowledge as a basis I'm sure you can learn it self-taught.
Bruce Mitchell's A Guide to Old English is good for a start.