Carnegie Mellon's Open Learning Initiative (OLI)

I've recently been reviewing Carnegie Mellon's OLI. It has some interesting models of instruction. The first thing I noticed is it's free, or that there is an open version of it. Apparently, "the Open & Free Version of the online course does NOT include
access to the end-of-module graded exams or to the course instructor.
No credit is awarded for completing the Open & Free Version of
the course." While the paid version, is:

Academic Version

The
Academic Version
is offered through educational institutions for credit awarded by the
student's home institution. Students in the Academic Version have
access to the same course material as the students in the Open &
Free Version PLUS access to the graded exams. The Academic Version
tracks student learning of key concepts and gives the student and the
instructor formative feedback to improve learning outcomes.

What's very interesting, besides the business model it it comes with a tutor. Here is a video describing the phyiscs tutor and the courseware.
I likethat they've tried to reduce the amount of interaction between the learner and the instructor, such that it can be learned without an instructor. But with the instructor, a learner get's more individualized learning from a human who can view the results with the tutor.