Running Linux? Whatever floats your boat man.
Of course, not every computer on the web is a desktop (or laptop) PC. There are numerous embedded devices. Linux, as you know, is merely a kernel. So I could very easily run it on, say, a kiosk, a toaster, or a dedicated terminal in which running a GUI would be impossible or a waste of resources. Same goes for Unix, BSD, or any number of other operating systems running without a GUI.