I would just like to say that there have been numerous encyclopedias released by fans of published books. JK Rowling doesn't have the right to stop soemone from creating an encyclopedia about her books. Even if she is creating one herself the one that Steven Vander Ark would release would not even equate to the success that JK Rowlings encyclopedia would. 

He is not taking the characters and giving them new storylines or changing events that already happened in the books he is simply just defining certain spells, places and meanings in Harry Potter his OWN opinion. Whereas when Rowling's Enclyclopedia is released it will be actual FACT not opinion.

I don't think Rowling is being greedy, I just think that she is being selfish because she knows that this encyclopedia will at best sell a few million copies where as her books have sold hundreds of millions. I think she wants to keep Harry Potter all for herself, but if she really wanted that she would have not PUBLISHED her works in the first place. When that is done your work is free for the public to interpret.