$teaser is now $view_mode in quiz.module, quiz_view() implementation on of hook_view()

The implementation of hook_view starts at line 964. The D6 version of the function is commented out and uses 3 arguments ($node, $teaser, and $page), the D7 version only uses 2 arguments ($node and $view_mode).

Adding one line of code after line 966 makes the check at line 982 work again:
if ($view_mode == 'teaser') $teaser = TRUE;

The check at 982 switches between a start form button and a link to the quiz.