Alan wrote:

> þá mun eg þín láta að njóta
> then I will cause you to benefit

I think Njáll is saying rather: "then I will cause you to be benefited
by" / "then I'll cause the benefit of you to be had" = "then Lýtingur
will enjoy the benefit you (i.e. "then he'll benefit from having you
as a kinsman - because otherwise, I wouldn't make any settlement at
all)". Hence MM & HP: "But if I offer any chance of a settlement, I
do it for your sake alone."

'njóta' takes a genitive object to express what someone gets to enjoy
the benefit of. Where 'njóta' is used as a finite verb, the subject
(i.e. the person who derives/enjoys the benefit) is nominative.

'ef þú sverðs né nytir, þess er ek sjalfr gerða'
"if you hadn't had the benefit of the sword that I made"
(Fáfnismál)

'ætla ek, at þú nýtir eigi boga minn'
"I doubt you'll be able to use my bow"
(Hemskringla: Saga Sigurðar Jórsalafara, Eysteins ok Ólafs)

In our example from Njáls saga, 'njóta' is a passive or impersonal
infinitive; no subject is expressed. If the subject of the infinitive
'njóta' was made explicit here, it would have to be put into the
accusative, as in the following examples:

'og væntir mig að hinir smærri menn og alþýða muni gott til leggja með
þér og láta þig njóta þess er þú varst þeirra formælandi'
"and I expect that the lesser men and the common people will speak
well of you and give you the benefit of the fact that you were their
spokesman"
(Þorsteins saga Síðu-Hallssonar)

'þá mun ég [...] láta þig njóta arfleifðar Jakobs föður þíns'
"then I will [...] cause you to enjoy the inheritance of your father
Jacob."
(Isaiah 58:14)