Copy values from taxonomy term field to new text field in content-type
According to me you can achieve it by doing something like:

Creating a PHP script which: Get all terms related to a node and then create a comma separated value for them and then store this as value of your new field in database.

You need to iterate over all nodes and the run following code to get all terms 

$result = db_query(
SELECT ttd.tid, ttd.vid, ttd.name, ttd.description, ttd.weight
FROM taxonomy_term_data AS ttd
INNER JOIN taxonomy_index ti ON ti.tid = ttd.tid
WHERE ti.nid= :nid
ORDER BY ttd.weight, ttd.name',array(':nid' =&gt;$node-&gt;nid));


Or you can use Drupal code as well for doing the same

$node = node_load(arg(1));
if ($node != NULL) {
$field = $node-&gt;field_my_vocabulary;
$lang= $node-&gt;language;
$terms_all = $field[$lang];
foreach ($terms_all as $term) {
$terms[] = $term['tid'];
}
return implode('+', $terms);
}


Now assign this vale to you new field.

The above code is not tested by me, but I hope it can do what you want with no/little modification :)