I did use virtualbox and inside a virtual windows xp I did install the free (in price) vmware server. Vmware server did not complain not to be run inside a virtual machine. But... virtualbox crashed, the windows just closed with status aborted.
Imho the possibility to run a virtual machine inside another proves 100% emulation.
You can also try to run qemu inside virtualbox, or virtualbox inside virtualbox.
If this would work, I think also most other programs would run without any problems.