If you are interested in the Vietnam War, or MOOCs, or have nothing better to do for the next six weeks, feel free to join the class. There is no cost or obligation with enrollment, and you are free to participate or lurk as you choose.
Hope to see a few TT-ers next week (I know one regular who has joined, but his secret identity shall forever remain so).
The course is designed like a survey undergraduate class for non-majors. Students who successfully complete the course earn a completion certificate, which is useful for items like continuing education credits. At this point college credit to accredited universities is not directly tied to courses like this, but down the road this will be a possibility (some MOOC providers are already connected with certain universities, but not all MOOCs translate into credit).
Some people use MOOCs to brush up on topics, while others use MOOCs as a way to see if they are prepared to handle college-level work, especially if they have been away from school for a while. So feel free to drop in and see if the class has benefit to you.