You're asking about the forum "style" or "skin", right? (As the word "service" doesn't really fit the context of your question.) The forum style is a mildly-customized vBulletin 3.something style. (Bottom of page)
What you see is only the tip of the iceberg, though......
I think vBulletin must either be: fairly difficult to dramatically change the style -or- be limited by its license. Most of the vBulletin boards I've come across are immediately identifiable since they look so similar.
I think the reason may lean toward the former. Looking at the html, there's an awful lot of inline CSS.