You can configure OpenSearch to use a search engine proxy.
    OpenSearch is a collection of simple formats for sharing search string results, in
      order to extend existing schemas such as ATOM or RSS. The list of registered search engines is
      in /config/alfresco/web-scripts-config.xml. You can configure a search
      engine proxy so that the OpenSearch client indirectly submits a search request through the SkyVault Content Services Web Server (the proxy),
      rather than directly to the search engine. 
    - 
        Create a new file called
            /config/alfresco/extension/web-scripts-config-custom.xml.
        
This file will contain the search engine proxy information.
 - 
        Create a new search engine proxy, using the proxy attribute.  For
          example:
        
<engine label="SkyVault Open Source Talk" proxy="opentalk"> <url type="application/rss+xml">http://blogs.alfresco.com/opentalk/ os-query?s={searchTerms}&itemstart={startIndex?}&itempage={startPage?} &itemlimit={count?}</url> </engine>The value of the proxy attribute must be a unique name that identifies the search engine.
 - Save /config/alfresco/extension/web-scripts-config-custom.xml.