I was waiting for someone else to post, but nobody has, so here I am again. I have two points to make about this song.

1. If you don't watch out, the narrator begins to sound creepy. I'm not going to write a whole essay on this, but when the verses go on and on, and he starts singing about how she wanted a man with land instead of him, it gets neurotic. It begins to change from a song about a man in love to a song about a man with an obsession. Don't let it.

2. The third tune that I just described is that rare thing, a purely modal tune. It is Mixolydian, using the fifth, rather than the tonic as its home tone. It's in the key of B-flat, but it begins on F, ends on F and has a prominent (both high and long) F in the middle. There's a G which is higher, but it's only an eighth note in a pick-up, so it doesn't count.

When I encounter a "modal" tune nowadays, it tends to start modal and then end on the tonic, to make a hybrid.

I don't know why abcnotation gives a version that is so high, but it's nice for recorder and flute - and perhaps for Vienna choirboy.
If you transpose it to a new key, it will still be Mixolydian modal.