The information returned by get_current_user() seems to depend on the platform.
Using PHP 5.1.1 running as CGI with IIS 5.0 on Windows NT, get_current_user() returns the owner of the process running the script, *not* the owner of the script itself.
It's easy to test - create a file containing:
<?php
echo get_current_user();
?>
Then access it through the browser. I get: IUSR_MACHINE, the Internet Guest Account on Windows, which is certainly not the owner of the script.