Is the Nocturnal Illusion remake legally for D/L anywhere?

Nowhere NEAR the same level of horrible.

Anyway, Mugen Yasoukyoku’s scenario was written by Mitsumine Nao, who also wrote Kanan. Tanashi Eizou and Yayoi Midori drew the art (in both cases, Mugen Yasoukyoku was the only notable game they worked on.)

Moegi Kazumichi was responsible for the music- again, Mugen Yasoukyoku is the only eroge he made music for.

EDIT: This site contains all that information and a lot more. Bookmark it.

Pseudonyms were common then and are still common now. Except, unlike with seiyuu, we generally don’t know their real names.
It is a known fact that Mitsumine Nao was the main writer, although whether that’s his real name or not is another question entirely.