Not quite free. Fair enough, as there are costs involved and some barrier is needed to prevent greedy/gratuitous signups.
“Application Processing Fee
Applicants are charged an Application Processing Fee in the range of $10 to $50 based on their country of residence. Students unable to pay these processing fees are eligible to apply for a scholarship.
Exam Processing Fee
Students are charged an Exam Processing Fee of $100 per end-of-course exam. Students unable to pay this processing fee are eligible to apply for a scholarship.”