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You can't do that by changing the template, since the real name is not being provided to the template.
Edit modules/system/blocks/system_blocks.php, and in the function b_system_newmembers_show (line 269 in version 2.0.5.2), change:
$block['users'][$i]['name'] = $newmembers[$i]->getVar('uname');
to:
$block['users'][$i]['name'] = $newmembers[$i]->getVar('name');