Well looking at the Members List, it's Dolby, Kudane, Cairenn, and then Remelio. Dolby was #1, Kudane #3, Cairenn #6, and Remelio #412. Why the skip in numbers? Who was Remelio? Looking at his avatar and some of his posts, I'd suspect that he was a part of the staff at some point in time. What happened to him?
Assuming Remelio was a staff member, it looks like
Olethros et Teleute was the first real member.
EDIT: Reading a bit farther, it seems Remelio and Cairenn were the first 2 to staff the WoWInterface site while Dolby and Kudane were still mainly at the EQ sites.
Cool stuff.
Let's start a WoWInterface history lesson!