No this is definitively not a Microsoft thing, but a license restriction of Metastock 10 that isn't mentioned anywhere. Thus, just don't buy Metastock 10 if you're willing to execute it in a virtual machine!!!
I would have been a new user of Metastock and was about to evaluate it. But it doesn't work in my environment ... if somebody knows a way to execute it in VMware, then please tell me ...