ok, so now I know why we can't use .htaccess in /forum folder

another test. just enable vBET again, add this htaccess in main folder (replace with the old one (NOT IN /FORUM FOLDER)):
Code:
# Comment the following line (add '#' at the beginning)
# to disable mod_rewrite functions.
# Please note: you still need to disable the hack in
# the vBSEO control panel to stop url rewrites.
RewriteEngine On

# Some servers require the Rewritebase directive to be
# enabled (remove '#' at the beginning to activate)
# Please note: when enabled, you must include the path
# to your root vB folder (i.e. RewriteBase /forums/)
#RewriteBase /


#RewriteCond %{HTTP_HOST} !^www\.hj-research\.com
RewriteCond %{HTTP_HOST} !(^www\.hj-research\.com$|^cdn\.hj-research\.com$)
RewriteRule (.*) http://www.hj-research.com/$1 [R=301,L]

#RewriteCond %{HTTP_HOST} !^www\.yourdomain\.com
#RewriteRule (.*) http://www.yourdomain.com/forum/$1 [L,R=301]

RewriteRule ^forum/((urllist|sitemap_).*\.(xml|txt)(\.gz)?)$ forum/vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L]

#vbet translator rules start

RewriteRule ^forum/?(af|sq|ar|hy|az|eu|be|bg|ca|zh-CN|hr|cs|da|nl|en|et|tl|fi|fr|gl|ka|de|el|ht|iw|hi|hu|is|id|ga|it|ja|ko|lv|lt|mk|ms|mt|no|fa|pl|pt|ro|ru|sr|sk|sl|es|sw|sv|zh-TW|th|tr|uk|ur|vi|cy|yi)/$ forum/vbenterprisetranslator_seo.php?vbet_lang=$1&redirected=/ [L,QSA]
RewriteRule ^forum/?(af|sq|ar|hy|az|eu|be|bg|ca|zh-CN|hr|cs|da|nl|en|et|tl|fi|fr|gl|ka|de|el|ht|iw|hi|hu|is|id|ga|it|ja|ko|lv|lt|mk|ms|mt|no|fa|pl|pt|ro|ru|sr|sk|sl|es|sw|sv|zh-TW|th|tr|uk|ur|vi|cy|yi)/(.*)?$ forum/vbenterprisetranslator_seo.php?vbet_lang=$1&redirected=/$2 [L,QSA]

RewriteCond %{REQUEST_URI} !(admincp/|modcp/|vbseo_sitemap/|cron)
RewriteRule ^forum/((archive/)?(.*.php(/.*)?))$ forum/vbenterprisetranslator_seo.php [L,QSA]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !^(admincp|modcp|clientscript|cpstyles|images)/
RewriteRule ^(.+)$ forum/vbenterprisetranslator_seo.php [L,QSA]

#vbet translator rules end


RewriteCond %{REQUEST_URI} !(media/|admincp/|modcp/|cron|vbseo_sitemap)
RewriteRule ^forum/((archive/)?(.*\.php(/.*)?))$ forum/vbseo.php [L,QSA]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !/(media|admincp|modcp|clientscript|cpstyles|images)/
RewriteRule ^(.+)$ forum/vbseo.php [L,QSA]

## Expires
<ifModule mod_expires.c>
	ExpiresActive On
	ExpiresDefault "access plus 1 seconds"
	ExpiresByType text/html "access plus 1 seconds"
	ExpiresByType image/gif "access plus 3456000 seconds"
	ExpiresByType image/jpeg "access plus 3456000 seconds"
	ExpiresByType image/png "access plus 3456000 seconds"
	ExpiresByType text/css "access plus 3456000 seconds"
	ExpiresByType text/javascript "access plus 3456000 seconds"
	ExpiresByType application/javascript "access plus 3456000 seconds"
	ExpiresByType application/x-javascript "access plus 3456000 seconds"
</ifModule>

## Compression
<ifmodule mod_headers.c>
	<ifmodule mod_deflate.c>
		AddOutputFilterByType DEFLATE text/html text/css text/xml application/x-javascript
		BrowserMatch ^Mozilla/4 gzip-only-text/html
		BrowserMatch ^Mozilla/4\.0[678] no-gzip
		BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
	</ifmodule>
</ifmodule>

#Remove index.php from hj-research.com/index.php
#rewrite engine on 
RewriteCond %{THE_REQUEST} index\.php
RewriteCond %{QUERY_STRING} ^$
RewriteRule ^index\.php$ / [L,R=301]
as you know with this htaccess vbet is working only on forum pages.
test it. and check that google can see your sitemap

thanks