Quoting from the SWsoft official announcement:
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All future releases of SWsoft’s Virtuozzo management tools will include support for other vendors’ virtualization solutions, including VMware virtual servers – giving data center managers unprecedented control of virtualized resources and enabling them to use various virtualization technologies without being tied to a single vendor’s management tools.
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SWsoft will introduce its first wave of support of another technology later this year with VMware virtual machine management. Xen and other technologies will soon follow…
The announcement is clearly referring to Virtuozzo 4.0 which is expected later this year. Meanwhile you may want to check the virtualization.info review of SWsoft Virtuozzo for Windows 3.5.1.