Have you reached out to Tim? I know him and I believe he wouldn't do that intentionally. Maybe he is busy with something else or just lost track of the schedule.
Of course he's been busy. Everyone is busy. But charging $200 (or $100 with coupon) for a course which is delayed for more than 1.5 years and still has no sign of completion is another story.
Side note: I've finished Build your own Redis in C/C++ (https://leanpub.com/build_your_own_redis) and it's pretty decent. The title of the book is a bit weird since it's almost 100% C++ so I don't know why they put "C" in there. But it's a pretty decent book (and reasonably priced).
Your support for creators is very much appreciated. There is now light at the end of the tunnel. More info here. https://news.ycombinator.com/item?id=41907594