Like for EDX, it is possible to take coursera courses for free. Here is a short example.
Login (or register if you have no account). Go to the course you want to attend to, in this example I take “Programming Languages, Part A”. Please note that the option described here are not possible for all courses.
On the course page select “Enroll”:
In the pop-up choose “Full course. No certificate” and continue.
And you can start: