vat-4.0 is currently under alpha-test. Snapshots of progressively more stable source trees are placed in the alpha-test FTP directory, along with binaries for requested architectures. Each snapshot is given a new alpha version number to distinguish them, e.g., 4.0a1, 4.01a2, etc. If you'd like to participate in the testing, help yourself to the contents of the alpha-test directory and send a note to vat@ee.lbl.gov indicating that you are an alpha-tester.
As an alpha-tester, you should expect to encounter bugs and odd behavior, and it is your responsibility to report these problems to vat@ee.lbl.gov. Please do not use these alpha versions to broadcast public events. Once v4.0 is stable enough, we will issue the general public release and announce availability on the AVT Working Group mailing list (rem-conf@es.net).