Well, kind of but not really. Xen isn't really bare metal in any sense of the phrase. It's just at a similar (but different) level of abstraction. In an embedded system you will need to have device drivers, respond to hardware interrupts, etc. On Xen you make hypercalls.

So eLua and these projects are similar in, say, the same way that a typical RTOS is similar to running Linux on AWS. They both have kernels, but the environments are vastly different.

Thanks for the explanation. I was really hoping to find something like the SqueakNOS project

http://www.artima.com/weblogs/viewpost.jsp?thread=239339

ROS calls itself a 'meta-operating system', I guess the definition of an OS is sort of blurry!