Looks neat, but I'm a little confused at what it's goal is. How is this different from, for example, supervisord?

Svsh provides a shell for already existing and running supervisors, specifically runit, daemontools, s6 and perp, which are all part of a "family" of similar supervisors. Svsh is external to them, it isn't a supervisor of its own, it just provides a better(?) interface to them.

I actually wrote it because, after switching from supervisord to perp, I was missing the shell provided with supervisord (supervisorctl).

I'm not 100% sure cause the details are a little weirdly worded. But I believe this is for monitoring already running tools like supervisord.

I guess I could try to post a better description of it on the website. The text basically assumes the reader is familiar with the supported supervisors, and that's probably not the best assumption.

It's orthogonal. It's a shell for interacting with daemontools, runit, s6, and perp each of which is a supervisord like tool.