apply processing only to forms with limited entries

// http://www.gravityhelp.com/forums/topic/display-number-of-form-entries-left-per-form
add_filter('gform_pre_render', 'show_entries_left');
function show_entries_left($form) {
    // see if this form has a limit set and we need to show how many are left
    if(empty($form['limitEntriesCount'])) {
        return $form;
    }
    // limit is set; continue processing
    else {
        // get the number of entries for this form
        $entry_count = RGFormsModel::get_lead_count($form['id'], "", null, null, null, null);

        // subtract the entry count from the limit to determine how many are left
        $left =  $form['limitEntriesCount'] - $entry_count;

        // append the number of entries left to the description displayed before the form
        $form['description'] .= "Hurry! Only <strong>$left</strong> more entries will be accepted.";

        // return the form
        return $form;
    }
}