punbb older version

hmm.. sorry maybe this is not in the right place..
but I really need older version of punbb (my priority is the first punbb)
the reason?
I am beginner in php programming, and I just feel I lost my train to this forum..
I wanna learn this forum from the beginning, because recent punbb are too complicated for me..
so where can I get the source for the first punbb??

thank you...

sorry my english