The IBM AIX Software Toolbox download page includes a package for MySQL 3.23, but that was a little bit too aged for my purposes. Fortunately MySQL distributes binaries for IBM AIX here:

That package will work out of the box with 5.3 as well. Download it, and unpack it to /usr/local:

root@server# cat mysql-5.0.45-aix5.2-powerpc-64bit.tar.gz|gunzip|tar xvC /usr/local
root@server# ln -s /usr/local/mysql-5.0.45-aix5.2-powerpc-64bit /usr/local/mysql

There is a file named INSTALL-BINARY which includes these instructions as well as some more information, but here's a quick overview of the things you need to take care of.

Create a user and group for privilege separation:

root@server# groupadd mysql
root@server# useradd -g mysql mysql
root@server# chown -R mysql:mysql /usr/local/mysql-5.0.45-aix5.2-powerpc-64bit

Create the MySQL data directory and initialize the grant tables:

root@server# cd /usr/local/mysql
root@server# ./scripts/mysql_install_db --user=mysql

Only the data directory need to be owned by the mysql user, so for security reasons, we will give all other files back to root:

root@server# chown -R root /usr/local/mysql-5.0.45-aix5.2-powerpc-64bit
root@server# chown -R mysql /usr/local/mysql-5.0.45-aix5.2-powerpc-64bit/data

Start it up:

root@server# /usr/local/mysql/bin/mysqld_safe --user=mysql &