It would be nice if the build-appliance image could generate an ova package in the OVF format along side vmdk disk images, as this would make it easier to use on a wider range of VMs. Seems like quite a low-hanging fruit, it should be just a matter of adding the ovf xml description, the ova package itself is just a tarball. For the OVF documentation links see http://www.vmware.com/technical-resources/virtualization-topics/virtual-appliances/ovf
I think that we did have ovf files at one point and while its supposed to be a standard, there were some problems with it cross platform! We can investigate again, would welcome patches
It is currently possible to run BuildAppliance images using vmPlayer and VirtualBox. The Build Appliance package contains the file Yocto_Build_Appliance.vmx. It should be possible to convert this file using VMware OVF Tool if one needs the .OVA file. As the Build Appliance is being gradually deprecated, I am closing this issue (enhancement) as RESOLVED/WONTFIX.