>> Hversu líkar þér nú skyrtan?
>> How do you like the new shirt?

> This would have to mean: "How do you like the shirt
NOW." "How do you like the new shirt?" would be "Hversu
líkar þér nýja skyrtan?" (And in modern Icelandic we
would say "hvernig" rather than "hversu".

Ah yes, of course; I was led astray by the context here. Örvar-Oddr
has been given a new shirt. But maybe she's asking him how he likes
it *now* after hearing her describe its making in verse.

>> Gerið sem þér líkar.
>> Do as you please.

> This is slightly odd. One would either expect
"gerðu (ger þú)" or "yður". Unless it actually
means "Do (plural) as you (singular) please".

This is from Völsunga saga. I found it in the Órðabók Háskólans text
database, which is matched by the version here [
http://www.snerpa.is/net/forn/volsung.htm ]. But there's another
online version which seems to keep to the spelling used by Guðni
Jónsson and Bjarni Vilhjálmsson:

Högni mælti: "Geri sem þér líkar. Glaðliga mun ek hér bíða þess, er
þér vilið at gera, ok þat muntu skilja, at eigi er hjarta mitt hrætt,
ok reynt hefi ek fyrr harða hluti, ok var ek gjarn at þola mannraun,
þá er ek var ósárr. En nú eru vér mjök sárir, ok muntu einn ráða várum
skiptum." [
http://www.heimskringla.no/original/fornaldersagaene/volsungasaga.php ].

Could this `geri(ð)' be a typo for `ger' or `gerðu'? The rest of the
paragraph does shift between respectful plural (he's talking to King
Atli) and singular: þér vilið ... muntu. He also switches between
singular and plural in the first person: mun ek ... (etc.) ... eru
vér. (Jesse Byock translates "Do as you like.")

>> en fara máttu með oss, ef þér líkar.
>> but you can come with us if you like.

> "... if it pleases you" would probably be closer to
the meaning - but of course it would depend on the
context.

From Göngu-Hrólfs saga. Hermann Pálsson and Paul Edwards translate /
paraphrase: "Still you can join us if you want." I'm not sure that I
understand a distinction in meaning between English "if you like" and
"if it pleases you (to do so)" in the context of accepting someone's
request to join a pirate crew on a voyage, except that the latter
sounds more old-fashioned or a higher register, or extremely polite.

LN