It's highly doubtful you'll get the source for the face recognition from within MeeGo, as "open" as folks proclaimed it was, the apps were not subject to being open whatsoever in most cases.

A quick look around, I found face tracking and recognition online, a lot in GitHub which could be forked.

Tracking and detection
Object (and face) detection
Face recognition API

And many, many others. Good luck on your search though for the MeeGo sources - who knows, perhaps a disgruntled Nokia engineer might supply code to you.

But it seems as if webcam (with permissions) and JavaScript face tracking and detection has come a very long way since I last looked at it in 2012. Heck, I'm actually impressed with some of the features now available.