to bypass the gateway if only free downloadable content is in the cart, edit the following line in the webassist/plugins/shopping_cart/process_transaction.php file:
<?php
// if in test mode, skip all checkout code
if ($WAGLOBAL_Test_Mode != true) {
?>
to:
<?php
// if in test mode, skip all checkout code
if($WA_Store_Cart->GrandTotal() == 0) $WAGLOBAL_Test_Mode = true;
if ($WAGLOBAL_Test_Mode != true) {
?>