Simple, none at this point... Keep in mind that the UBB.Threads7 product was released only a short while ago, I know of no one who has taken the task into integrating into any CMS...

With that being said, UBB7 ships with its own news portal and customizable side blocks, which would cover half of what most CMS' supply.

If someone does take up a task of going towards this the most popular choices would be:
PostNuke, PHPNuke, e109, and a vast array of others wink

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