That code displays text saying something like "visit this product's web page" which is a link to a URL which you enter in the product editing page.

You can find the language file where TEXT_MORE_INFORMATION is defined and change it to "Crafter", or maybe to a chunk of code which will be interpreted when run to equal a product-specific image plus link.
Or you could insert said chunk of code somewhere in the
<?php echo sprintf(TEXT_MORE_INFORMATION, zen_href_link(...
statement.

I expect I could figure out the right formulation for that, but it would take a bit of research...
and some trial & error (hopefully not too much error ;)