Their is limited window-eyes support in a dos box.  You can get around, but
it is nothing like vocal-eyes and a hardware synthesizer.
Jfw in a dos box isn't much better, but jaws is free, and you can probably
find an old copy of asap which was great.  You still will need a hardware
synthesizer.
It depends on what your friend needs to do at dos.
You can run dos commands, but I think dos applications really want dos
screen readers to work well.