$ sudo apt-get update
$ sudo apt-get install gnuboy-sdl 

gnuboy-sdl is installed in your system.

Make ensure the gnuboy-sdl package were installed using the commands given below,

$ sudo dpkg-query -l | grep gnuboy-sdl *

You will get with gnuboy-sdl package name, version, architecture and description in a table

gnuboy-sdl package basic information: