I was able to get captcha working for everyone in the contact us form. If you go to ow_plugins/contactus/controller/contact.php. Remove lines 90,91, and 96. This "If" statement keeps the captcha from displaying for registered members. With this removed it will display the captcha field for everyone.
Be sure you go to ow_includes/config.php, and set dev mode to true. Once you have removed the lines save the file, go to your site, and refresh any page. Set dev mode back to false. I have attached a screenshot that shows the lines.
step by step:
1. open the config.php file in ow_includes, set dev mode at the very bottom to true, save the file.
2. open the contact. php file in ow_plugins/contactus/controller, remove lines 90,91, and 96,save the file.
3. Go to your site, refresh any page.
4. set dev mode back to false at the very bottom of the config.php file, and click save.
Your done. You will have to re-apply this when the plugin is updated.