Hi SamL. I'm not sure when the HTTP API will be released. However, for you and everyone else curious, an explanation is is order.
Here is a map of the tasks we're working on. (Click for larger version, or see attachment 1.)

Green = done
Yellow = in progress
White = not started
The blue circles denote areas we're actively working on. In order:
❶ One of our engineers, Johan, is implementing the underlying D-Bus API right now. The HTTP API (not pictured) will act as a wrapper for the D-Bus API, so as the timing works out, when the D-Bus API is done the HTTP API should be done as well. Johan has so far implemented reading the power controller for battery charge, and is currently porting reading/writing to our FPGA. Soon, we can do actual useful stuff with the API, but how soon is unknown. Johan hasn't done this before, and therefore can't produce an accurate estimate. I'm guessing it will take him at least few months to work through everything. Assuming we can get out some sort of gimped HTTP API built on that work, which won't run simultaneously with the touch-screen user interface on the camera, I would
very roughly estimate "late January" for basic HTTP control. This should not include video streaming, but should include video download and basic file management.
❷ I am continuing work on the new back-of-camera user interface. I've spent the last two weeks working on one of the two great unknowns of the process, jog wheel input. The other great unknown, the software keyboards, I will start work on tomorrow. I don't know how long the software keyboards will take. They could take a few days, or they could take a few weeks. The jog wheel still needs roughly a week or two of work, as each widget needs its own behaviour implemented. (Menus are going to become a
heck of a lot easier to select.

)
❸ Foobar has effectively ported the current UI forward to our shiny new Debian-based operating system. This is a
major milestone for us! It means we can abandon our old operating system, which was sucking up a lot of our time. It also means we can do a more piece-wise release of the new features as they're built out, so we may see useful parts of the HTTP API available well before the full HTTP API is finished.