So that's something.
You still have to purchase the game if you want to play but if you re-activate a vanilla WoW account you get Burning Crusade for free.
So is this enough for you to check out WoW if you haven't done so already? Personally, I've never played the game and paying a subscription is a big part of it. I feel like the ship has sailed for me at least and I don't really want to get into it this late in the game.