> Kjartan býst snemma fimmtadag í páskaviku ...

> Kjartan got ready early on the fifth day of Easter week (I
> assume this means something like the fifth day after
> Easter) ...

Fourth day after, actually: <páskavika> is the week
following Easter, and <fimmtidagr/fimmtudagr> is 'Thursday'.

> Guðrún mælti: "Gott skaplyndi hefðuð þér fengið ef þér
> væruð dætur einshvers bónda og láta hvorki að yður verða
> gagn né mein en slíka svívirðing og skömm sem Kjartan
> hefir yður gert þá sofið þér eigi að minna að hann ríði
> hér hjá garði við annan mann og hafa slíkir menn mikið
> svínsminni.

> Gudrun said: "You would have gotten a good disposition if
> you were a daughter of some farmer and cede neither that
> you be of use nor harm than such disgrace and shame as
> Kjartan has done you then don't sleep to remind of that he
> rode here by (the) house with another man and such men
> have a very short memory.

> Gudrun spoke, “You have got good dispositions if you were
> daughters of some farmer and do? neither (anything) that
> brings you advantage nor harm than such dishonor and shame
> as Kjartan has done you then you sleep not less that he
> rides here near (the) yard with one man and such men have
> great ??

> Guðrún spoke: “You (plural) would-have received good
> (commendable) disposition if you (plural) had-been
> daughters of some farmer and (they) let neither to be of
> use to you nor harm, but such dishonour and shame as
> Kjartan has rendered you, then you sleep not less that he
> rides here by (the) yard with another person (man) and
> such men have swine’s-memory.

The <að> in <að yður> seems to be Zoëga's sense A.IV(8) 'the
source of something': 'neither use nor harm from you lot'.
The real puzzle is <láta>. Based on form alone, the choices
seem to be infinitive, 3rd plur. pres. indic., or 1st sing.
pres. subj. The first seems impossible. I can't see
anything that looks like a reasonable plural subject, even
an implied one. My best guess, of which I'm by no means
certain, is that there’s an implied 'I', essentially 'and I
would get neither use nor harm from you lot'.

> Þykir mér og rekin von að þér þorið Kjartan heim að sækja
> ef þér þorið eigi að finna hann nú er hann fer við annan
> mann eða þriðja en þér sitjið heima og látið vænlega og
> eruð æ helsti margir."

> It seems to me also compelled hope that you have the
> courage to get Kjartan at home if you don't have the
> courage to find him now when he goes with another man or
> two, but you sit at home and lose promisingly and are
> always rather many."

> It seems to me also customarily done that you dare attack
> Kjartan at home if you dare not meet him now when he goes
> with another man or a third but you sit at home and behave
> hopefully and are always many more?

> (It) seems to me also a driven-off (futile) hope that you
> would-dare to seek (attack) Kjartan at home if you
> would-dare not meet him now when he travels with a second
> person (man) or a third, but you sit (stay) at home and
> behave promisingly and (but) you are always far too many.
> (there are too many of your type)”

At the end I think that she's not making a general statement
about a type, but rather simply saying she's fed up with
having too many of them always hanging about.

> Óspakur kvað hana mikið af taka en vera illt til mótmæla
> ...

> Ospakr said she said much and (it) is poor to contradict
> ...

> Ospak said she was making a big deal of it but (it would)
> be ill to contradict (her) ...

> Óspakr declared her to make (say) much of (it) but (and)
> (it) to be ill in the way of contradiction (ie hard to
> gainsay her) ...

I'd take that <en> to be definitely adversative, 'but', not
'and'.

Brian