Hi to all following these tutorials!
I initially had problems with my MySQL 4.0.20 installation where I would get errors like "Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)" or "040727 08:45:57 mysqld ended"
I found out that it was the MySQLStartItem that was at fault. Don't use the one that comes with 4.0.20.
Instead you should use Marc Liyanage's older version: http://www2.entropy.ch/download/mysql-startupitem.pkg.tar.gz
When I installed that one, everything worked fine and I could restart the machine and MySQL would start up automatcially just fine.
Of course if everything worked out for you then that's great and you can just ignore this post. Btw, I'm on Jaguar on a DP-500MHZ G4. Cheers.