From the article:
While it was never a mere recreation, it expanded significantly over time. Nowadays, Turtle WoW differs from World of Warcraft with features like additional playable races, leveling zones, quests, endgame content, and transmogrification.
I think around the time Blizzard did their Season of Discovery for Classic WoW, I heard a lot of people talk about Turtle WoW and how they want something more like that (Classic+) and not just the old game anymore.
Dunno about that last part. According to some comments I've read, the head of this project has been doing some shady shit for years.
Running their own mount shop in-game, taking other people's work without permission, selling gold, whatever.