2
open edituser.php
find on (or around) line 101:
$edituser->setVar('name', $_POST['name']);
change to:
$edituser->setVar('name', $name, true);
find on line 169(or thereabouts) :
$name_text = new XoopsFormText(_US_REALNAME, 'name', 30, 60, $xoopsUser->getVar('name', 'E'));
$form->addElement($name_text);
change to:
$name_text = new XoopsFormLabel(_US_REALNAME, $xoopsUser->getVar('name'));
$form->addElement($name_text);
save and you're done.