I'm not sure if this is true, but the last I heard you weren't allowed to change your forum name in anyway. Although I've seen it happening with the exception of a few people lately, I'm not particularly sure if you're allowed to or not... unless it says somewhere on the forum otherwise that you're allowed to, but who knows!
Hope this gave you some information about it, Jambo
Hello, in extension to what Jambo has told you - I believe you CAN have your forum name changed, but you need to have a valid and applicable reason for the admins to do so - That's what I've heard, at least.
Hope I helped to make things a little clearer, if you ever need anything feel free to pop me a PM on the forums or in-game.