Since it's written in assembler, shouldn't this virus be more properly called an "x86 virus" rather than a "Windows virus" or a "Linux virus"?
I think the distinction is because it understands how to infect both sorts of executable files. Some other x86 operating system - e.g., OS X, BeOS, whatever - would presumably not be vulnerable.
Exactly. This isn't going to work very well on a PowerPC or Sparc machine running Linux.