I am not really sure what you are wanting to do, but if your entire vB suit is in the forums directory then you could just follow the above post and move it to the root if you wanted.
However, You could follow that article you mentioned aswell ("How to install CMS in Root, Forums in subdirectory"). But to be honest I wouldn't do that if I were you. Better keep things simple for the long run. I'm sure there are other ways you could achieve the main CMS Homepage on (
http://www.site.com ) and your forums in /forums (
http://www.site.com/forums/) if thats what you wanted.
But either way, it should work, totally up to you