It works if you already have an account. I think anyone who watches one of my videos from today forward is out of luck.
I'm also a course creator (but I don't use cloud9). A change like this is a really big deal for someone in his/her shoes. Having to re-record all of those videos is non-trivial, and doing it with the self hosted version would still require new videos to be made.
I feel for them, but it is the risk associated with using any sort of product you don't directly manage yourself.
You can version pin/host/containerize to self host, whatever, along with sharable prebuilt envs.