Newell doesn't directly refer to the in-development engine as "Source Engine 2, " so it's possible (albeit unlikely) that he's referring to a separate engine altogether, or (even more unlikely) Valve has more than one game engine being created.
"Help us turn Defcad into the world's first unblockable, open-source search engine for 3D printable parts, " says Mr Wilson in the video posted on the website looking for funding.