Re: Transfering wpmu 2.71/ bpress 1.01 / and bbpress to new domain.
A. On your Hosting Control Panel point the new URL to the same folder as where you have everything now. Then go to the admin settings and change the URL on both WPMU and BBPress. It will log you out and you have to log in. Install plugin broken link checker https://wordpress.org/extend/plugins/broken-link-checker/ and have fun changing all the URLs.
there is another option it involves setting up a new SQL and exporting everything and importing… bbpress has a pluging for you to export and import, I never used it so I don’t want to recommend it.