I added some fixes to the phpbb_mysql.sql at least to let the script create all the original categories, but it’s not enough.
When processing topics/posts there is just a long list of the type:
Parent post [some id] doesn't exist. Skipping [some id]
and, of course, there are no posts imported.
I wonder if anyone could confirm that the default scripts don’t work with phpBB 3.3.3 tables?