Wow, that's a really nice board system... I don't really see why they call it the "extreme message board" but I really like how fast it loads, and the skin they have running for their forum (http://forums.xmbforum.com) is very nice, I would guess it's the default.
Re: XMB Forum - Great Forum, and Easy Installation. You can customize this forum alo
Tried it, and I never really liked it, granted it is a couple years ago now so things could have changed.
They lack of (easy) customization, there are mods, but when I used it all mods required chaging of sourcecode (and in template files), and if you had a couple of them it was never easy to find exactly where to make the changes. And on every upgrade you had to redo all moddings.
Skinning just means changing colors in that forum, at least when I tried it couple years back, but frankly the supportforum looks exactly the same as it did then so I guess its still only colorchanges possible.