Ok...
Its possible but still one little problem  
 
First the way to get phpads working in the phpbb forum
Open /includes/pager_header.php 
Put this code in it:
Code:
if (!isset($forum_row['forum_name'])) { 
    $bannerwhat = "nokeywords"; 
   } else { 
    $bannerwhat = $forum_row['forum_name']; 
} 
$bannerwhat = str_replace(" ", "+", $bannerwhat); 
$template->assign_var('KEYWORD', $bannerwhat); 
Open in your Template-map /phpBB2/templates/templatename/ the template-Dat "overall_header.tpl" and put in this code
Code:<table width="100%" border="0" cellspacing="0" cellpadding="0"> 
<tr> 
<td> 
<a href='http://PathToYourAdServer/adclick.php?n=....' target='_blank'><img src='http://PathToYourAdServer/adview.php?what={KEYWORD}&n=...' border='0' alt=''></a> 
</td> 
</tr> 
</table> 
U have the make banners in phpads with keywords. Your keyword must be exactly the same as your forum name. So if u have a subforum called "all about cars" make your banner with keyword "all about cars"
When theres no banner with that keyword it will go for the keyword "nokeywords", u can make a banner for that as well
This will work, but....
I installed the seomod, cause of this code i got a little problem:
Code:# 
#-----[ OPEN ]------------------------------------------ 
# 
viewforum.php 
# 
#-----[ FIND ]------------------------------------------ 
#
$page_title = $lang['View_forum'] . ' - ' . $forum_row['forum_name'];
# 
#-----[ REPLACE WITH ]------------------------------------ 
#
$page_title = $forum_row['forum_name'];
When it opens viewtopic it cant find the forumname anymore. Cause of this code the solution described above doesnt work anymore for the viewtopic. Does anybody know who i can change that without losing that part of the seomod?
Greetz 
stan