this theme here at vbulletintempates is not free, however it is sold by
http://www.vbulletinstyles.com for 24 dollars
it is a very nice skin and is being updated constantly by Saintdog as the new relases come out.
the price is not bad considering the cost of a professional skin for just your own forum would be hundereds if not a few thousand.
however buying vBulletin is the best forum software there is.
the skins are not released for free, or not all of them because of the time it takes to develop them. i personally just spent 2 weeks making a skin. and it would be worth about 1200 for just one forum to keep it for them self and not release it to anyone.