virtualbox.org

As I can see, VirtualBox 1.4.0 is released, but I can't find any version for mac.

On the changelog, the first line says,

General: added support for OS X hosts

What this means?

The Mac host is still beta. We plan to do a beta 2 next week (version 1.4.1) with USB support. The Mac will be part of the standard release cycle once it has left the beta test phase (i.e. when all features have been implemented).