More precisly:
For Windows Vista, key Visual Basic 6.0 runtime files are shipping as a part of the operating system and will be supported for the lifetime of Windows Vista.

'....

Binaries that do not ship on Windows Vista will follow their planned support lifetime. These files are being tested for compatibility as part of our testing of Visual Basic 6.0 applications running on Windows Vista, but they will need to be deployed by the application setup and will not be supported as part of Windows Vista. The list of runtime files distributed with Vista can be found below.
So you see, its not supported but is tested on.