A .vmx file is just a text configuration file containing the settings for a VMWare virtual machine. (HDD type, HDD image path, hardware devices/settings, etc).
Looking around on Google, it may be possible to create a new virtual machine in Virtualbox, and use the .vmdk disk image that came with the simulator. Obviously that means installing Virtualbox and I've never tried using a VMware disk image in Virtualbox on FreeBSD (I've no idea if it'll work either).
As it appears the simulator is provided as a fully blown virtual machine, I don't see any mileage in trying to access the .vmdk file directly. (Assuming your intention is to actually use the simulator)