SculptGL is available on the chrome web store and you can find the source code here.
If you want to download a standalone version, you can do it here (please note that the web version is updated more often !).
Sketchfab made a fork of the old SculptGL version with a new design : Sculptfab.
Fahd Arshad, Hassan Mehmood and Fauzan Raza also made fork of the old Sculptgl version with kinect controls and a kinect friendly interface : Hephaestus.