First opt-in, then opt-out, our-way-or-the-highway next. As usual. Fortunately, emigrating from Github is not entirely hard, if that were to happen. (Yes, I feel the need for a disclaimer "this is all speculative"; alas)
Moving a git repo is easy, but have you found any "not entirely hard" way to export Issues from GitHub? All I've found so far is essentially "here's an API, build it yourself".