string credit_str;

text my_credits
{
string = credit_str;
...
}

function something
{
while(showing_credits)
{
my_credits.pos_y += time_step * scroll_speed_of_credits;
...
wait(1);
}
}

Something like this.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt