IPBoard 3.4.1 Mod-Rewrite
 

So IPBoard is telling me to put this in:

If yes, add a file called .htaccess with the following contents.
<IfModule mod_rewrite.c>
Options -MultiViews
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule \.(jpeg|jpg|gif|png)$ /public/404.php [NC,L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

Do I just drop this in .htaccess under the html root or what and is the code here compatible with litespeed?

yes. just as you do under apache.