Sæll Símon.

Good questions as usually.

> Many thanks for another fascinating text. One thing I'm not
> completely clear on: were Sigurður and Hárekr there to buy a
> ring for themselves or for the king?

Themselves.

> ek hefi ekki á því tekit - why á því and not just það here?
> It's not partitive is it, surely? After all, the whole amount
> is involved.

The phrasal verb 'taka á e-u' means "touch".

The verb 'taka' has many idiomatic ways of usage.

http://www.northvegr.org/zoega/431.html

> þeir eru stolnir fénu - thanks for the note,
> I needed that little extra hint to realise that
> it means "they were robbed (rather than stolen here)
> OF the money. Am I right?

Exactly.

> sem var at sitja um þat fram er markaðrinn stóð - is
> there an equivalent of Modern Icelandic's "vera að gera"
> present continous tense here? (this becomes past continuous
> when a past tense form of vera is used). I'm afraid I don't
> understand the um þat fram at all. Ah - could sitja um be
> something like, well, sit around (idle)?

I should have put 'sem var' within commas.

"Þetta þótti mörgum manni vanhagr mikill,
sem var, at sitja um þat fram er markaðrinn stóð."

Does that help?

> Þá áttu Norðmenn stefnu sín - surely stefnu sína, as
> it's fem. accus. sing.? Or could it be a genitive going
> with (á) milli?

The latter.

> ráðlaus - does this mean foolish, or lacking good counsel,
> or even panicky, i.e. being unable to hear good counsel?
> Very interesting in view of the English king Ethelred the
> Unready - this has nothing to do with not being
> prepared, but is rather connected with ráð.

"Counsel-less."

Zoega gives "shiftless, having lost one's head"

http://www.northvegr.org/zoega/332.html

> ef þetta yrði framgengt - acted upon or successful?

Something closer to the latter.

Bestu kveðjur,
Haukur