Just wanted to say thanks, TheBlackCat, for posting some links. I also searched a while, but couldn't find any relevant links (probably because I don't know what to look/search for, rather than them simply not existing).
Also wanted to point out that your second link provides no sources. While I normally wouldn't care so much, since there's no mention of the actual implementation (i.e., software stack), it's hard to come to a conclusion either way about whether it runs "on the metal" or not, only that it runs Linux. (which is still impressive, don't get me wrong) Same with the third link.
I wish news/tech outlets like that would put more work into their articles; it really rubs me the wrong way when I'm interested in something and I can't find the answer because someone was too lazy to include sources for their information. Sort of defeats the point of reading their articles when you go there to learn and can't.
I honestly wouldn't be surprised if they were running on the metal, but I just can't come to that conclusion using the information in those two links. The first and fourth are pretty good, however.