Only the [PHP/Mapscript module installation](http://mapserver.org/installation/php.html) is documented on their site, and even then, not specific to Mac. Since the modules are bindings linked to the main `libmapserver.dylib` there doesn't seem to be anything via `pip` or `gem` (except maybe [ruby_mapscript](https://github.com/sourcepole/ruby_mapscript), but that's an unofficial third-party module).

I suppose that section of the caveats could just read:
```
Built mapscript modules are located in:
  #{opt_prefix}/mapscript/<language>
```
To me, that seems a bit harsh to just leave the Homebrew user without any form of install docs for the modules.