Probably when the developers are so rich they don't need money for food or rent.

Not to mention that there's nothing preventing a 3rd party from developing an open source patch implementing support for this very feature.

Sure there is: lack of expertise. Also, unfamiliarity with the code base. For people without programming experience, there's also the opportunity cost of learning a programming language.

The reason open source hasn't taken off with the general public is b/c every time a non-programmer suggests a genuinely useful feature (to non-programmers), the response is: "it's open source, program it yourself." Most often, the easier and cheaper path is to just buy the competing commercial program.

I'm not really sure what your point is here…the feature is _already_ available in closed-source form. I was merely pointing out that its presence and that of an open source implementation are not mutually exclusive simply because the closed source version was developed by the same people who developed and released the source for the rest of VirtualBox.

Wont they be working at Oracle soon?

Maybe. Or maybe Oracle will stick with its own Xen-derived OracleVM.

And you think that uncle Larry will make them rich?