From the source code:

https://github.com/koalaman/shellcheck/blob/master/ShellChec...

shellForExecutable "sh" = return Sh

shellForExecutable "ash" = return Sh

shellForExecutable "dash" = return Sh

shellForExecutable "ksh" = return Ksh

shellForExecutable "ksh88" = return Ksh

shellForExecutable "ksh93" = return Ksh

shellForExecutable "zsh" = return Zsh

shellForExecutable "bash" = return Bash

shellForExecutable _ = Nothing

Their about page[0] says "ShellCheck is a static analysis and linting tool for sh/bash scripts."

[0]http://www.shellcheck.net/about.html

It's pretty clearly a play on words...

I don't get it, what's it playing on?

Its name might be a play on "spellcheck". When I first read it quickly, my eyes bounced over the "h" and my brain filled in a "p".

Personally, I enjoy cleverness like this.

idk if it's a play on something -- but all of the things you mentioned above are still called a "shell", even if it's not the standard "sh" shell.

and, from parts of the source code, it appears it may work with ksh, zsh, etc. (i don't have a sample handy to try though).

not for me, I use rc