meta & keyword site içeriğine göre, test etmeye henüz fırsat bulamadım ama ilk denememde çalışıyordu:

##############################################################
## MOD Title: phpBB SEO Dynamic Metatags
## 
## MOD Author: dcz <n/a> http://www.phpbb-seo.com/
##
## MOD Description: Generates dynamic metatags for phpBB.
##
## MOD Version: 0.0.1
##
## Installation Level: Easy
## Installation Time: 2 Minutes
## Files To Edit: (2)
##            includes/page_header.php,
##            templates/subSilver/overall_header.tpl
##
## Included Files: n/a
##
## License: http://opensource.org/licenses/gpl-license.php GNU General Public License v2
##############################################################
## Author Notes:
##
## You can edit the amount of keywords outputted for topics by editing the number in this line:
## AND t.topic_id = $meta_topic_id LIMIT 20";
## Part of this code inspired from -http://www.phpbb.de/viewtopic.php?t=49679 Larsneo and Titus (@phpbb.de)
## You SHOULD NOT use more than 20 keywords in the keyword meta tags
## As well, you SHOULD NOT use too long description tags
##
##############################################################
## MOD History:
##
##	2006-10-06 - First released version
##
##
##############################################################
## Before Adding This MOD To Your Forum, You Should Back Up All Files Related To This MOD
##############################################################

#
#-----[ OPEN ]------------------------------------------
#

includes/page_header.php

#
#-----[ FIND ]------------------------------------------
#

define('HEADER_INC', TRUE);

#
#-----[ AFTER, ADD  ]------------------------------------------
# If you use the phpbbstyle.com sql cache system, just look for //SQL CACHE and 
# uncomment (and comment) the proper lines
# Also, make sure you change FEW_MORE_KEYWORDS_COMA_SEPARATED, YOUR_DEFAUT_DESCRITPION, 
# YOUR_DEFAULT_KEYWORDS_COMA_SEPARATED, YOUR_AUTHOR_INFOS & YOUR_COPYRIGHT_INFOS with the proper infos.
# Note : YOUR_AUTHOR_INFOS & YOUR_COPYRIGHT_INFOS lines are commented by default, because it is not 
# needed in most cases. Uncomment the proper lines if you want those to be outputted as well.

//BEGIN www.phpBB-SEO.com Dynamic meta tags
if ( isset($HTTP_GET_VARS[POST_TOPIC_URL]) ) {
	$meta_topic_id = intval($HTTP_GET_VARS[POST_TOPIC_URL]);
} elseif ( isset($HTTP_GET_VARS[POST_FORUM_URL]) ) {
	$meta_forum_id = intval($HTTP_GET_VARS[POST_FORUM_URL]);
} elseif ( isset($HTTP_GET_VARS[POST_CAT_URL]) ) {
	$meta_cat_id = intval($HTTP_GET_VARS[POST_CAT_URL]);
}
if ( isset($meta_topic_id) ) {
	$sql = "SELECT c.cat_title, f.forum_name, t.topic_title
                FROM " . TOPICS_TABLE . " t, " . FORUMS_TABLE . " f, " . CATEGORIES_TABLE . " c
                WHERE f.forum_id = t.forum_id
                AND c.cat_id = f.cat_id
                AND t.topic_id = $meta_topic_id";
        if( ($result = $db->sql_query($sql)) ) {
		if ( $meta_row = $db->sql_fetchrow($result) ) {
			$description = $board_config['sitename'] . ' :: ' . $meta_row['cat_title'] . ' :: ' . $meta_row['forum_name'] . ' :: ' . $meta_row['topic_title'];
		}
        }
        $sql = "SELECT w.word_text
                FROM " . TOPICS_TABLE . " t, " . SEARCH_MATCH_TABLE . " m, " . SEARCH_WORD_TABLE . " w
                WHERE t.topic_first_post_id = m.post_id
                AND m.word_id = w.word_id
                AND t.topic_id = $meta_topic_id LIMIT 20";
        if( ($result = $db->sql_query($sql)) ) {
		$keywords = '';
		while ( $meta_row = $db->sql_fetchrow($result) ) {
			$keywords .= ($keywords == '') ? $meta_row['word_text'] : ',' . $meta_row['word_text'];
		}
        }
} elseif ( isset($meta_forum_id) ) {
	$sql = "SELECT c.cat_title, f.forum_name
                FROM " . FORUMS_TABLE . " f, " . CATEGORIES_TABLE . " c
                WHERE c.cat_id = f.cat_id
                AND f.forum_id = $meta_forum_id";
	//SQL CACHE
       	if( ($result = $db->sql_query($sql)) ) {
	//if( ($result = $db->sql_query($sql, false, 'META_')) ) {
		if ( $meta_row = $db->sql_fetchrow($result) ) {
			$description = $board_config['sitename'] . ' :: ' . $meta_row['cat_title'] . ' :: ' . $meta_row['forum_name'];
			$keywords = $board_config['sitename'] . ', ' . $meta_row['cat_title'] . ', ' . $meta_row['forum_name'] . ', FEW_MORE_KEYWORDS_COMA_SEPARATED';
		}
		//here we clear $result from ram and cache it
		$db->sql_freeresult($result);
		//End sql cache opt
       	}
} elseif ( isset($meta_cat_id) ) {
	$sql = "SELECT cat_title
                FROM " . CATEGORIES_TABLE . "
                WHERE cat_id = $meta_cat_id";
	//SQL CACHE
        if( ($result = $db->sql_query($sql)) ) {
	//if( ($result = $db->sql_query($sql, false, 'META_')) ) {
		if ( $meta_row = $db->sql_fetchrow($result) ) {
			$keywords = $board_config['sitename'] . ', ' . $meta_row['cat_title'] . ', FEW_MORE_KEYWORDS_COMA_SEPARATED';
			$description = $board_config['sitename'] . ' :: ' . $meta_row['cat_title'];
		}
		//here we clear $result from ram and cache it
		$db->sql_freeresult($result);
		//End sql cache opt
	}
} else {
	$description .= 'YOUR_DEFAUT_DESCRITPION';
	$keywords = 'YOUR_DEFAULT_KEYWORDS_COMA_SEPARATED';
}
$phpbb_meta  = '<meta name="title" content="' . $page_title .'">' . "\n";
//$meta_str .= '<meta name="author" content=" YOUR_AUTHOR_INFOS ">' . "\n";
//$meta_str .= '<meta name="copyright" content=" YOUR_COPYRIGHT_INFOS ">' . "\n";
$phpbb_meta .= '<meta name="keywords" content="' . $keywords  .'">' . "\n";
$phpbb_meta .= '<meta name="description" lang="fr" content="'. $description .'">' . "\n";
$phpbb_meta .= '<meta name="category" content="general">' . "\n";
$phpbb_meta .= '<meta name="robots" content="index, follow">' . "\n";
//END  www.phpBB-SEO.com Dynamic meta tags

#
#-----[ FIND ]------------------------------------------------
#
	'PAGE_TITLE' => $page_title,

#
#-----[ AFTER, ADD ]------------------------------------------
#
	//BEGIN www.phpBB-SEO.com Dynamic meta tags
	'META_TAG' => $phpbb_meta,
	//END www.phpBB-SEO.com Dynamic meta tags	

#
#-----[ OPEN ]------------------------------------------------
#
templates/subSilver/overall_header.tpl

#
#-----[ FIND ]------------------------------------------------
#
<META http-equiv="Content-Style-Type" content="text/css" />

#
#-----[ AFTER, ADD ]------------------------------------------
#

{META_TAG}

#
#---[ SAVE/CLOSE ALL FILES ]-----------------------
#
# eom
Bu ve benzeri bir çok bilgi: phpBB SEO, site dili için üzgünüm.