I've recently wanted to write a streaming download service like this recently. The great thing about your service is that although it's a proof of concept of a handful of neat tricks, the core functionality works perfectly and could be extremely useful. This makes it faster than ever to drop upload links in a chat room and effectively solves the problem in https://xkcd.com/949/.

Is the backend licensed as free software? It would be fantastic for admins to host their own version of this since it allows the concept to propagate without worry of shutting down.