It's "cheating" though in the sense that it's against a TOS on a website, but tons of things are against a TOS and almost no one reads them. They're pretending to be one, but Coursera is not a college, is not accredited and does not hand out degrees. This is a free online self-study course being taken by hundreds of thousands of people with varying degrees of seriousness. Some people may treat it like a college course and want the certificate (for what I am not sure), but I bet most people just want the knowledge. I signed up for a similar course once and never logged in because my schedule changed, should I get an F and have that publicized?
I have also worked through some iOS courses from Standford on iTunes U and I would not think twice about helping someone with one of the problems. Is that cheating?