I am not sure about the exact release date. But you can contact support@wolfram.com to request for a developer account if possible.
Accessing this online API does indeed work well: http://online.wolfram.com/api/shenghui/demo/f?conv=6&dis=-3&icos=-1&sep=0.2
Get a Mathematica online account for development if you do not have
Since this short tutorial was posted today, when will this be possible for the public?
