Professor Direct is run by a company called Straighterline, a host of self-paced online courses.
Professor Direct allows instructors to establish the value of the course they offer, by establishing the size of the cohort, the services they will provide and the price point for these services. The company charges a base fee and instructors add their price to this. StraighterLine also offers instructors commissions for attracting students.
Read more about it in this post from the Chronicle of Higher Education