I'm sure it's custom there are knock-offs though just search google http://forum-skins.com/free-forum-skins/digital-point-vbulletin-theme/
The DP theme is pretty close to the stock vB4 theme. It looks like they just changed the colors, and maybe added some different post icons. It woudn't be hard to do yourself if you wanted.... just change all the stock blue tones to shades of green and teal.
hm it wouldn't hard but if we tried to make, it will take time .. but time makes your worked perfect as u need.
It is pretty similar just with different colours, however they have added a few modifications that they did themselves I believe.
This theme is available for free in vb.org. Not sure whether its just the same. Will update my post after finding the link in vb.org
You can use vBulletin's theme editor and see if it'll match DP's theme. Only the plugins and modifications won't be the same cause they are customs, unless you pay someone to do it for you. But yeah, DP is using about 90% of the default theme.