From the Drupal website drupal.org; “Drupal is an open source content management platform powering millions of websites and applications. It’s built, used, and supported by an active and diverse community of people around the world.”
The OPAC module aims to allow a Drupal page to effectively become an OPAC+. Again from the Drupal website; “The opac module enables libraries to integrate their catalog into Drupal allowing importing records, make advanced searches with faceted results, circulation task etc … This module is intended to work with any ILS by using connectors. Everyone can make its own by creating a php file.”
This is a example of one of the benefits of Free and Open Source Software, users are able to adapt components to suit their needs, and share the results.
I am not a Drupal user but have been enthused enough to ‘dip my toe’ in the Drupal water.