Sourceforge has been unreachable for part of the day on June 6th, 2009.
This could be verified using DownForEveryOneOrJustMe.Com.
If you want to download BT747 explicitally, you can use one of the download mirror sites.
While Sourceforge is not really up at the time of writing, they did manage to make information available on the site.
The Sourceforge staff thinks they had a database related failure, and they are making extra backups before proceding with bringing the site fully online again.