Hi Leeneia -

Nope, that F natural is actually correct (you'll hear it if you click their audio link at the top). You find a lot of that kind of thing in van Eyck and Susato too, a tonality which is really of that age. That note can certainly be played as an F# but I like the slight surprise of the flattened-then-raised tone, and it is in period. You'll see the same natural-to-sharp relationship in that passage in the original score too, twice (it's in the repeat as well). The tune was probably already old when Arbeau noted it down.

Regarding the second link, for the melody you play only the Superius line, which means the tune goes over several pages. In the original score (which is actually in soprano clef: I was looking at the wrong line) if you think of the key as being B minor in the dorian mode (i.e. the key signature of A with its three sharps) you can just play it as normal. In another part of the music, I see that the leading tone is natural the first time the phrase appears, but raised in the repeat. This sort of thing often happens in early music, and I have heard it performed both ways - with A natural followed by A sharp, and also with A sharp both times (which I tend to prefer, but maybe that's just because we're all accustomed to modern tonality).