I'm guessing this is supposed to be 1HS since there is also a Forged Deathsteel Two Handed Sword. My guess would be a typo, but I've never seen one so I could be wrong.
Incorrect, they can USE 2handers, just cannot gain skill in it. There are a few weaps usable by classes that can't skill up in them, do a database search and you will see.
However, as it is a long sword, I would expect it to be 1hs... was kinda hoping to get 2hs on my warr up, though... for weighted axe pulling, of course.