There /is/ a modern, well-managed open-registration shell and IRC service, similar to what you're talking about, called Hashbang. You can join via https://hashbang.sh.

We're reasonably active, and we have almost 1400 registered users [edited: i was corrected by a hashbang admin as to the amount].

The ultimate purpose of hashbang is to expose more users to a traditional remote UNIX server and command line, as well as teaching people how to use it. We've created a slight barrier to entry with the intentionally obtuse signup flow, as we don't want completely non-technical users flooding the service.

I promise we won't bite :D