Spent a couple minutes poking around at kanban-like alternatives/supplements to labeling:
GitHub uses this and Huboard internally for some projects. Supported by Rally, so probably not going away anytime soon.
GitHub uses this and Waffle internally for some projects.
Looks interesting. (Marking issues from the command-line? Sweet!) It's also pricey.
Chrome plugin. It's free, so could be worth an experiment.
Free, easy to use. No direct GitHub integration -- would need to use IFTTT or Zapier, and might be suboptimal still.
After the exchange in https://twitter.com/kyleashipley/status/852855137634791424, I created https://github.com/waldyrious/github-kanban-boards preserving the commits here, and initiated its transfer to @shipstar.