How can I get a checkbox to return True/False?
It depends how you want to use the true/false value. 

Case 1

You could change the data in a validation handler. In hook_form_alter, something like:

$form['#validate'][] = 'my_great_handler';


Then:

function my_great_handler($form, &amp;form_state){
  $form_state['values']['checkbox1'][LANGUAGE_NONE][0]['value'] 
    = ($form_state['values']['checkbox1'][LANGUAGE_NONE][0]['value'] == 1);
}


Not sure what that would do for you, though.

Case 2

If you want to show users true/false rather than 1 or 0, you could change that in a template. Create a template for the field, and add something like:

Checkbox: &lt;?php print $checkbox1 == 1 ? 'True' : 'False'; ?&gt;


Case 3

If you want to save the data in a custom data store, you would add similar code right before the save, in hook_node_save, or some such.