Last week's LinuxWorld Conference in Boston was the locus of several important announcements. Again, virtualization was front and center. In no particular order:

* XenSource announced XenEnterprise. Where the free Xen hypervisor provides bare-iron virtualization hypervisor to run multiple virtual operating systems on top of Intel and AMD hardware, the commercial product XenEnterprise provides much-needed management functions for deployment, provisioning, and management of virtual environments built on the Xen hypervisor. XenEnterprise is due for release by July.

* Virtual Iron announced that Version 3 of its virtualization software will provide management for the Xen hypervisor. Among the several "free as in beer" announcements at LinuxWorld, Virtual Iron said the single-server versions of Virtual Iron Version 3 will be available without charge for personal and limited commercial use. The first beta release (for Linux) is due in July.

* Desktop management vendor Altiris announced the release of its application virtualization product, Software Virtualization Solution (SVS). SVS allows applications to be installed under Windows, while isolating application files, registry settings etc., from the underlying operating system. SVS is free for personal use, and available immediately for download from Altiris' site and from Tucows.com.

* Not to be outdone, Microsoft announced that it would make its popular operating system virtualization product Virtual Server 2005 R2 free, after charging up to $999 for it last year. It is available immediately for download from Microsoft's Web site. VWare's competitive operating system virtualization product, VMware Server, has been free since February this year, and is available for download at VMWare's Web site.

* XenSource also announced it has licensed Microsoft's Virtual Hard Disk (VHD) format - the format Microsoft uses to store its Virtual Server images. This will allow XenSource users to import, manage, and recover virtual machines created with Microsoft Virtual Server. Meanwhile, VMWare will make its virtual machine disk format openly available, downloadable, and free of charge. Microsoft's VHD format is already openly available under a royalty-free license.

* Finally, in a welcome move, Microsoft announced that it would support Linux as a guest operating system on Virtual Server 2005 R2. Less welcome is the news that Service Pack 1 for Virtual Server R2 will not be available until early 2007.