It works if you already have an account. I think anyone who watches one of my videos from today forward is out of luck.

What's stopping you from setting up your own c9 setup since it is open source?

Probably because he/she has tons of videos that walk through setting it up on c9.io's old site.

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'm not saying it isn't a hassle. But that is a better solution then rerecording everything. If you come up with a self hosted solution for c9, I would hope that the courses have a single video for setting up cloud9 which would be better then rerecording everything.

I feel for them, but it is the risk associated with using any sort of product you don't directly manage yourself.

This. Yes.

Consider Eclipse Che and CodeEnvy.

You can version pin/host/containerize to self host, whatever, along with sharable prebuilt envs.

For how long, is the question...