...
VirtualBox provides a variety of ways to get at the core functionality. From Approximately from least to most grungy:
VBox gui (canned program). It exports nearly the complete API. I used it to create Scientific Linux 5 and Scientific Linux 6 VMs (after downloading ISO images from the SL web site) and use it routinely to monitor VM activity. It's fine for interactive use; not appropriate for running batch jobs on VM
...
VirtualBox shell - extensible python interface. Have not yet tried it, but probably should. It's only barely mentioned in the SDK document, but it looks like the source is installed as a Python site package.
Web service - exports nearly complete API. Can be used via Java, Python, or as raw web service. I don't think it's appropriate for us. We don't need the ability to control VMs remotely; I expect VM commands will be issued from the host.
...