figured it out.. it must be before all other properties... and is a url relativr 

<?php

$uploader->LicenseUrl="/support/phpfileuploader/license/phpuploader_fcpost-IP.lic";
$uploader=new PhpUploader();
$uploader->MaxSizeKB=2150400;
$uploader->Name="myuploader";
$uploader->MultipleFilesUpload=true;