>>We're using vBulletin

>
>Any special reason it will use a closed source product? Are there no
>open source web forums that will do?

Three reasons.  First PHPBB is the closest open source product available but history has shown that security and features in PHPBB is significantly lacking compared with the closed source products being used.  Second vBulletin is the most ubiquitous web forum software in use today so a lot of people are used to it's features and interface.  Third is pure supportability.  vBulletin is fully supported by the company that owns it for updates/security/etc.  which is extremely important in an environment like this where you want optimal up time.

You'll notice that the existing boards that are coming together for this project are all using closed source product for their forums.