The WordPress blogs should be cached with WP Super Cache but not the forums because the sites use the Xenscripts bridge.
WordPress 3.3.1 Multisite in root
XenForo in /community
XenScripts bridge (not compatible with caching)
I downloaded and installed the latest development version. Under the advanced settings tab [wp-admin/network/settings.php?page=wpsupercache&tab=settings], locate the place to add strings to exclude URLs (near bottom of the page), enter your relative path to the forums.
In checking the source after browsing to the pages, the blogs are being cached but the forums are not.
Please let me know if you agree, if this is helpful, or if you see a way to improve the steps. Maybe you know a better way to make sure the forums are not cached by WP Super Cache.