This is rad, however, echoing others it does seem a bit risky to trust that Github won't swap out. For stuff like boards, it'd be nice to have an option sync with Trello. Worst case scenario all of the data is there and usable without a lot of fuss.
That said, Trello sync is an interesting idea. Taking a look at Trello integration is somewhere on our list, mostly to set up a Trello-to-ZenHub importer but sync would be a nice side-effect. Thanks for the feedback!