If he got Ollie's permission (which he didn't) to make an improvement on the map, and he said so in the map description
Permission? You don't own any maps you do to WL, nor should you and you don't morally need permission. And it was quite transformative. Almost all maps are plagiarisms of something anyway, but noone cares unless it's a WL player.
However it's just good practice to list your sources for stuff.