edX is no longer offering honor code certificates. There is no certificate for those on the audit track (free). If you wish to get a certificate, then you need to enroll as a verified student by the deadline (pay the fee and verify your identity) and pass the course.
The reason there are no more free certificates is that it is important to know that the person who earned the certificate is who they say they are, and there is an administrative cost associated with the process used to verify your identify. The discontinued free honor code certificates did not have the verification step and caused confusion with the verified certificate, and hence edX stopped offering it. Instead, edX now offers financial assistance for verified certificates for those who cannot afford the certificate fee.
Learners can still view course materials for free on edX including all videos, discussions, and practice activities. Audit learners do not have access to graded activities (see edX's enrollment model for more information). Audit students can use their Progress page to show enrollment in this course.