Umm...what about this?
HTML Code:
<if condition='THIS_SCRIPT == 'forumdisplay' AND $foruminfo[description]"><meta name="description" content="$foruminfo[description]" /><else />
<meta name="description" content="$vboptions[description]" /></if>
or... define them separately in SHOWTHREAD and FORUMDISPLAY, and have the following in headinclude:
HTML Code:
<if condition="THIS_SCRIPT != 'showthread' AND THIS_SCRIPT != 'forumdisplay'"><meta name="keywords" content="$vboptions[keywords]" />
An excellent SEO tutorial can be found at
http://forum.time2dine.co.nz/showthread.php?t=98
Where does the $foruminfo[description] come from that you are using on FORUMHOME?
There's usually several forums displayed there...