I am getting the same problem. Terms and Conditions only show for admin. If guest user checking out, it just shows n/a.
I am using Drupal 5, Ubercart 1.6
I figured it out. It's the check_markup function (http://api.drupal.org/api/function/check_markup) that does not allow access to anonymous users (depending on the filters and permissions you have set up).
What I did was go thru uc_gtct.module and search for the string
check_markup
Then change that string to add ,$check = FALSE at the end so that the check_markup function does not check if user has permission check the markup!
So this line
'#value' => check_markup(variable_get('uc_gtct_term_conditions_text', 'not set'),variable_get('uc_gtct_term_conditions_format', 3)),Becomes:
'#value' => check_markup(variable_get('uc_gtct_term_conditions_text', 'not set'),variable_get('uc_gtct_term_conditions_format', 3),$check = FALSE),