It is not preventing you to load your forum in https you can change your forum URL from ACP>Configuration>Site details and change you forum URL with https then you need o change your .htaccess file to redirect you https whenever some one tries to enter with http
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
Remove www. from second line if your forum does not included www.