>>111 のパッチを改めて更新しますた．で，httpd.conf に入れる設定はこんな感じか．
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LoadModule charset_lite_module libexec/apache2/mod_charset_lite.so

<Location /*/dat-utf8/*.dat>
    SetOutputFilter XLATEOUT
    CharsetSourceEnc CP932
    CharsetDefault UTF-8
    CharsetOptions NoImplicitAdd IgnoreIlSeq
    AddDefaultCharset UTF-8
    Header append Cache-Control max-age=5
</Location>
<Location /test/bbs-utf8.cgi>
    SetInputFilter XLATEIN
    CharsetSourceEnc CP932
    CharsetDefault UTF-8
    CharsetOptions NoImplicitAdd IgnoreIlSeq
</Location>

<VirtualHost ...>
    # ServerName dso.2ch.net のところ
    AliasMatch ^/(\w+)/dat-utf8/(\d+\.dat)$ /home/ch2dso/public_html/$1/dat/$2
    Alias /test/bbs-utf8.cgi /home/ch2dso/public_html/test/bbs.cgi
</VirtualHost>
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ブラウザ振り分けの RewriteCond / RewriteRule なんかは .htaccess でもよさそうということで．