I guess it depends if you consider the act of writing to be something that can only be done by a human. If a program can produce a work that passes as "writing"

I guess it depends if you consider the act of writing to be something that can only be done by a human. If a program can produce a work that passes as "writing", then that program could be called the "author" of the work. So a student that takes said output and hands it in is plagiarizing by claiming credit for something written by a different "author". It'll probably take some time for language to evolve around non-human agents. There's no intrinsic reason to prefer separating (or combining) that terminology by humanness of agent, afaik. At least, for common usage. One will win and only time will tell.