Seems not to work

Thanks for reporting this. Just to document how these modules work, the problem lies with the mapping between the GET qeury parameters that Drupal uses for pagination (page=) and the parameters that the Nutch search application expects (start=). To fix this mapping, the settings page from the OpenSearch Client module lets you enter a URL template. The one I'm using for Drupalsearch.com is this:

http://localhost/nutch/opensearch?query={searchTerms}&start={startIndex}&hitsPerSite=0&hitsPerPage=10

The OpenSearch Client module takes the Drupal parameter, page, and multiplies it by however many results are supposed to be returned (10), and substitutes the {startIndex} placeholder with that number.

And there is in fact a bug somewhere because on DrupalSearch.com, it isn't working.