The com_esearch component normally the 'of' path off your
web site to fetch the enterprise search engine specific
code and return a common format.

In the 'of' directory of the zip release file are the fetch
modules for different enterprise search engines.

These files need to be placed at:
    http://www.myplace.com/of

Omnifind - IBM Omnifind Yahoo Edition
     http://omnifind.ibm.yahoo.net/

Indri - UMass search engine
     http://www.lemurproject.org/

For test purposes you can use, http://www.tnrsearch.com/testof/fetch.php 

Note: this is not a full search engine