An open label study is one in which each  patient knows whether he/she is taking the placebo (or nothing) or the active drug, and the medical staff also know who is getting what.

Perhaps Don will explain why they have chosen this design during the webcast. It's easier to organise than a placebo controlled double blind trial, and that may be the reason. But the downside is that the FDA would probably want a second controlled double blind study to confirm a positive result.