Head Tracking with Cliffs of Dover

[Novotny]

Well - and I'm entirely guessing here - perhaps NP used obvious and well known coding routines in the basics of their code, whilst their clever stuff existed at a higher level.

A bit like building a house. You can't copyright the concepts of foundations and brickwork, however you could sue someone if they knocked off a replica of your pride and joy, 'Cool House 1.0'.

I hope that makes some sense, I'm totally guessing and trying to get a feel for the issues.