They generally don't let people audit courses (ie, non-credit) for free. Maybe if you're an employee of the institution, or have a connection, but if you go through the registration process you'll have to pay.

I audited a course at Harvard Extension, and the professor said she wouldn't grade the work of auditing students. You could do the assignments, and attend the lectures, but you'd get no feedback.

hmmm that makes sense, why would she want to do work for free? she is paid to teach paying students and help them improve. my parents are both college professors, and they get paid for online courses based on the # of enrolled students i think.

interesting...