I've edited the files.. copied the english folder and named it nl
everything is translated
edit: it doesn't show, but I guess that is because there isn't a dutch frontpage yet?
edit2: I got it to work, just a little change in the template

here are the files:
modul.lang.php<?php
/**
* Translation file for Modul - Contact Mail
* Language: Dutch
* Locale: nl
*
* Copyright (C) Kevin Papst.
*
* For further information go to
http://www.bigace.de/ *
* @version $Id: modul.lang.php,v 1.4 2006/11/26 21:58:51 kpapst Exp $
* @author Kevin Papst
*/
$LANG['name'] = 'Stuur contact email';
$LANG['title'] = 'Stuur ons een bericht';
$LANG['description'] = 'Laat een bericht achter voor een of meer ontvangers.';
?>
translation.lang.php<?php
/**
* Translation file for Modul - Contact Mail
*
* Language: Dutch
* Locale: nl
*
* Copyright (C) Kevin Papst.
*
* For further information go to
http://www.bigace.de/ *
* @version $Id: translation.lang.php,v 1.3 2008/03/14 00:32:59 kpapst Exp $
* @author Kevin Papst
* @package bigace.translation
*/
$LANG['initial_message'] = '';
$LANG['initial_subject'] = '';
$LANG['create_new_msg'] = 'Maak nieuwe e-mail';
$LANG['contact_error_msg'] = '<p><b>Fout!</b></p><p>Sorry, je e-mail kon niet verzonden worden<br>Probeer alstublieft uw bericht nog eens te sturen.<br>Dank u wel</p>';
$LANG['error_retry'] = 'Probeer a.u.b. nog eens te verzenden';
$LANG['form_message'] = 'Bericht';
$LANG['form_subject'] = 'Onderwerp';
$LANG['form_email'] = 'Uw e-mail adres';
$LANG['form_name'] = 'Uw naam';
$LANG['form_send'] = 'verzenden';
$LANG['form_title'] = 'E-mail opstellen:';
$LANG['missing_values'] = 'Vul alstublieft de verplichte velden in';
$LANG['required'] = ' Verplichte velden';
$LANG['unconfigured'] = 'Deze module is niet correct geconfigureerd. Neem alstublieft contact op met uw Administrator.';
$LANG['email_intro'] = 'Het volgende bericht is naar u verzonden met het BIGACE Webmail Formulier.';
$LANG['email_sent'] = 'Uw e-mail is succesvol verzonden.';
?>