I think I understand what's happening with the out-of-the-box Borges examples.
WEBrick.rb includes Borges.rb, which in turn includes all of the individual
components including the Counter example. Counter.rb has

    class Borges::Counter < Borges::Component
      # ...

      register_application('counter')

    end

This means register_application gets called when the file is required. That
method registers the application with the default dispatcher, which is the
object responsible for recoginizing the '/counter' part of the URL.

The 'tutorial' app isn't registered because the require statements for that
one and a few others are commented out of the top-level Borges.rb file.

This means that in order to add your own application you can add it to
Borges.rb.

Thanks for listening, everyone.

Jim
-- 
Jim Menard, jimm / io.com, http://www.io.com/~jimm/
"Yes, I know /. is slanted. It still irritates me though."
    -- CrayzyJ on slashdot
"Well, if it wasn't slanted it'd be |."
    -- Eunuchswear on slashdot