Wouldn't it be acceptable to display a message along the lines of
"The DVD you have inserted cann't currently be played because the supporting software has not been installed. This is because it is not legal for Ubuntu to distribute this software in some countries. If you are certain that it is legal for you to install this software in your country, you can install it now. Would you like to install it now?
Wouldn't it be acceptable to display a message along the lines of
"The DVD you have inserted cann't currently be played because the supporting software has not been installed. This is because it is not legal for Ubuntu to distribute this software in some countries. If you are certain that it is legal for you to install this software in your country, you can install it now. Would you like to install it now?
<yes button> <no button>"