I've been using Shadow for a year and that's exactly what it does. It's a standard windows box and you can install whatever you want on it, and there's no usage

I've been using Shadow for a year and that's exactly what it does. It's a standard windows box and you can install whatever you want on it, and there's no usage limits. I use it to play windows games on my mac without fussing with dual booting. I played through the Witcher 3 entirely on that machine. :) Non action games are playable over Wifi, but on a wired connection it's much better. It does have its own client and disconnects if you are idle so I don't think you could run it as a server, but I never tried. The only odd issue I ran into is that it supports a virtual USB device for pass-through which is cool, but you can't use a fancy multi-button mouse as that USB device because the mouse is "special" and it's always a 2 button virtual mouse but the xbox controller worked just fine. They do have a fairly slow rollout of new hardware updates and new country support at this point, and seemed to be in danger of going out of business for a while, but so far it's still there. You can always hook up something like Dropbox to back up work in progress.