I participated there and couldn't guess for the life of me how does Baez gathers the amount of energy needed to put together all the materials, setup all the exercises and review and comment all the participation in a tuition free everybody-welcomed online experience such as that, beyond his normal academic duties. In the link there are the e-lectures but all the online forum give-and-take is sadly lost.
John Baez' recent work on Mathematics of Tuning Systems is such a fun read. I enjoy how he explains ideas so clearly that the general public can understand and appreciate.