Didn't they say in the end that c9.io will continue to work?
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.