Digg.one is a clone of the wildly popular Digg News portal (V1/V2 Design).
Digg Sigma aka digg.one is built using modern web design and Exponential 6.x CMS powered by the 7x diggClone Social Networking Platform.
Digg Sigma is not digg.com nor is it any other site; Sigma is unique in it's own powerful features and stylish design UI.