> Bolli tók vel undir þetta ...

> Bolli took this well (how does "under" fit here?) ...

See Zoëga s.v. <taka> with preps.: <taka undir e-t með e-m>.
Here <með Kjarani> is understood.

> Bolli readily seconded this ...

> Bolli agreed well -to this (ie readily fell into line
> with, took this on board,warmed to the idea, took it under
> his wing) ...


> Viðræðu þeirra Kjartans hafði konungur fyrri spurt en
> borðin væru í brottu því að hann átti trúnað í hvers
> þeirra herbergi hinna heiðnu manna.

> Their, Kjartan's (and Bolli's) conversation had the king
> previously been informed of but the tables would be away
> (??) because he had a secret (spy?) in the lodgings of the
> heathen men.

> The king learnd of ir discussion, Kjartan’s (et al.)
> before the tables were (cleared) away because he had a
> trustee? in each of their, the heathen men’s, lodgings.

> (The) king had been informed of (the) conversation of
> them, Kjartan (and co) before the tables were (taken) away
> because he kept (eiga, Z5) a confidence (confidant (?) in
> (the) quarters of each of them (?) of the heathen men (I
> don´t think I have the syntax quite right but I suspect
> this is close to the meaning.)

I'd simply say 'in the lodgings/quarters of each of the
heathen men'. None of the available dictionaries offers
'confidant' or 'spy' as a possible translation of <trúnaðr>,
so either <hann átti trúnað> is to be understood either as
elliptical for <hann átti trúnaðarmann>, or <trúnaðr> 'a
secret' can include 'a person whose allegiance is secret'.
On the whole I prefer the first interpretation, but either
way, the meaning is pretty clear.

> (All good things come to those who feast)

So can a lot of bad things: I remember an SCA feast that was
aptly summed up as 'The chicken was green, and the broccoli
wasn't'!

> Konungur tók vel kveðju hans og kvaðst hafa spurt af hið
> ljósasta um hans erindi "og mun þér þetta mál auðsótt."

> The king received his greeting well and stated for himself
> to have been informed of the clarity concerning his
> business "and to you this matter will be easy to win."

> (The) king readily seconded his greeting and said he had
> learned most plainly of his errand “and this will be easy
> to do for you.”

> (The) king took (received) his greeting well and
> declared-of-himself to have been-informed of that,
> most-clearly, concerning his errand “and this matter will
> (be) for you easily-gained.”

I don't think that there is any 'of that': it appears to me
that <af hit ljósasta> is a unit, 'most clearly'.

> Konungur svarar og brosti við: "Já Kjartan," segir hann,
> "eigi mundi okkur hér um harðfæri skilja þótt þú værir
> nokkuru kaupdýrri."

> The king answers and smiles in reply: "Yes, Kjartan," he
> says, "to us would not here about (??) stubbornness
> discern although you were somewhat demanding a high
> price."

> (The) king answers with a smile, “Yes Kjartan,” says he
> “(it) would not (be) to us here regarding (that) hard to
> overcome decision? though you were something of an
> expensive purchase.”

> (The) king answers and smiled with (that) (as was his
> want!): “Yes, Kjartan,” he says, “(there) would not for us
> here be-differences (be-disagreement, see skilja, impers.
> Z5)

I think that you mean Z4.

> because of (over, um, Z10) stubbornness (ie we would not
> disagree with each other) even-if you were demanding-a-
> somewhat higher-price (comparative) (driving a harder
> bargain).”

I think that it's concessive, 'even though you were
demanding a somewhat higher price', rather than
hypothetical.

> Konungur lagði það til annan dag eftir.
> The king appointed that to the second day after.
> (The) king left it to the next day.
> (The) king committed to (?) that, the next day after.

As Alan evidently saw, <annan dag eftir> can't be the object
of <til>, since it's accusative, not genitive, so <til> must
go with the verb. I'm not sure of the exact shade of
meaning, but it must be something like 'committed to' or
'agreed to'.

> Líður nú vetur sjá.
> That winter now passes.
> Now that winter passes.
> Passes now this winter.

I'd go with 'the' or 'that' for <sjá>.

Brian