Does ko09 have a feature anything like "registers in Vim"?

Rationale

It would be nice to be able to store off values from userscripts without having to use the clipboard (and potentially clobbering a value that was supposed to be saved there).

Answer

Yes. One way this can be accomplished is with a KO userscript and the following component:

    Components.classes['@activestate.com/koPrefService;1']
          .getService(Components.interfaces.koIPrefService)
          .prefs
          ;

… to store off arbitrary values.

See also:

https://github.com/dreftymac/public.lab/blob/d44ee91b376b7b8cf9906df0c5ca6b2a6f2e71a3/demo/komodo8.demo/tymac_komodo_addon.js#L101

You can use ko/prefs for this, documented here:

http://docs.komodoide.com/SDK/api/commonjs/prefs