I do it for you, but I tend to think leading least on is better than just going ahead and fixing things.

The item your looking at is being included on the page as a template. ( in fact any inclusion that can be seen as {{pagename}} in the source of a page is known as a template in mediawiki.  You can find such pages by limiting a search to the template namespace.  So, your page is at http://wiki.koha-community.org/wiki/Template:DevBook and it explains how to modify it there.

If we were more clever we could use semantics to auto include a page in the devbook depending on its contents using dB like queries.

As a side note, you are not limited to only including templates on pages, you can in fact include any page on another page using {{namespace:page name}}.

Hope that helps.