Hi Jeanne,
Technically it would be possible to install BigBlueButton off-line, but we (the core developers) have never done it. On a newly setup Ubuntu 10.04 server, the install of BigBlueButton will trigger the download of over two hundred packages for dependencies, see
Recommend you install BigBlueButton when connected to the internet, then you can move the server inside a closed network. However, if your users are unable to access the internet, they will not be able to run the BigBlueButton client as the Flash framework will need to download some files from Adobe to run as well.
In short, to run BigBlueButton, both the server and the clients need to be connected to the internet.
Regards,... Fred
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BigBlueButton Developer
BigBlueButton on twitter: @bigbluebutton