eZJScore 1.5 no longer uses //index_ajax.php//.

Although this information has been updated in ezjscore 1.5 INSTALL doc that is shipped with the extension, it has not yet been updated in the http://doc.ez.no/eZ-Publish/Technical-manual/4.7/Installation/Virtual-host-setup/eZ-JS-Core-rewrite-rules 4.7 online documentation and in http://doc.ez.no/Extensions/eZ-Publish-extensions/eZ-JS-Core/Installation generic online documentation