I've used Heroku for over 7 years. Heroku's selling point is essentially devops-as-a-service. That's why they can get away with charging so much compared to the hosting competition. A "self-hostable Heroku" doesn't make sense, at least to me. With this, I'd have to do devops, like every other hosting platform. Granted, I did only scan the home page, so perhaps I'm missing something.