my forums have both posts that require users to login to view them, and also posts that anyone can view. I'm trying to SEO for it since its an inner page but thinking its not working. If I type in my sites name (in google) with forum after it the subdomain page pops up. Does this mean it can be SEO'ed? I'm a bit confused.
(almost) Everything with text on the web can be optimized for SEO. You can use htaccess redirect to "clone" the inner pages and add separate sitemap for that. That way spiders will have no trouble.