playBunny: Considering the rules don't define the MDU, nor does the game enforce it, I doubt that The player could not make a legal move with the second die refers to the MDU.
Note that the rule above mentions legal moves as well: If the player cannot make a legal move, he is notified about this situation by a message "You cannot make a move" and must pass this move to his/her opponent by performing an "empty" move - clicks on one of sending buttons. Such move is displayed as "pass" in the game notation.
(verstecken) Wenn du Spiele mit ähnlich starken Gegnern spielen willst, kannst du beim Erstellen eines neuen Spiels die BKR eingrenzen. So kann niemand ausserhalb des gewählten Ratings das Spiel annehmen und sehen. (Katechka) (zeige alle Tips)