It means that index.php is not in the same directory as global.php.
If you want to call the template from outside your forum directory you can try this instead:
PHP Code:
<?php
error_reporting(7);
chdir('/path/to/forums/directory/');
require('./global.php');
eval("dooutput(\"".gettemplate("donate")."\");");
?>
You will probably need to make all the header and footer links absolute (/forums/search.php), as well as the path to the images folder, to make everything work correctly.