How future-proof is this? i.e., where do we get updates from?

(if there aren't any extra APT repos, is there a source tree/recipe to upgrade to later versions?)

Currently this is more of an experiment to see if it is possible to get Docker running. The image is based on Raspbian with a custom kernel compiled for working with Docker and OverlayFS. We will publish our buildscript within a couple of days on github. Based on the feedback we get we want to provide updates to the image on a regular base.

Thanks. I would very much like to see that buildscript - I've been tinkering with the idea of building something along these lines but with an Ubuntu armhf userland (given that Ubuntu on ARM has a lot of advantages for me).

Just stay tuned. It is coming. :)

Any news on that build script?