On Linux, this is a simple addition to your ~/.Xmodmap:

    keycode 66 = Mode_switch
    keysym h = h H Left
    keysym j = j J Down
    keysym k = k K Up
    keysym l = l L Right
    keysym space = space space Return
    keysym y = y Y BackSpace
    keysym u = u U Next
    keysym i = i I Prior
    keysym o = o O Delete