Oracle has released a first beta for version 4.0.0 of the open source VirtualBox desktop virtualization application for x86 hardware. VirtualBox 4.0.0 Beta 1 features new settings and a disk file layout for VM portability, support for the Open Virtualization Format Archive (OVA) and a redesigned user interface with guest window preview and a new display mode. Support for asynchronous I/O for iSCSI, VMDK, VHD and Parallels images, as well as resizing VDI and VHD images has also been added. Other changes include support for more than 1.5/2 GB guest RAM on 32-bit hosts, the ability to copy files into a guest file system, support for the Intel ICH9 chip-set and a number of bug fixes.

Starting with version 4.0 the license for VirtualBox has changed. For the first time, both the base Oracle VM VirtualBox product source code and the binary are licensed under the GPLv2, while the Extension Pack mechanism, which allows third-party sources to add their own add-on functionality, is licensed under the PUEL. The change means that distributors shipping the Open Source Edition (OSE) of VirtualBox no longer need to build from the sources themselves.Strangely support for USB 2.0 host controller, VirtualBox RDP and PXE ROM support has been moved to an Extension pack, I suspect this move implies that at a later stage these features will become part of a premium package.

As with all development releases, use in production environments and on mission critical systems is not advised.