EDX courses can be taken for free. Of course then you will miss the certificate, but the content is the same. Also you have a time limit for viewing the content, but in my experience it is more than enough.
Here is a short example:
After logging in with your account (register if you do not have one) search for the course you want attend to.
For the example I choosed “Introduction to Cybersecurity”.
Choose “Enroll now” on the course page:
Scroll down a bit and choose “Audit this course”:
One the next page you can just start the course. A dialog might be shown that you can earn the certificate, you can just ignore that or choose “Explore the course” here:
Enjoy and keep learning!
We learn Security! 
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