For 1.2.3, you don't need to change anything. To use this book with version 1.3.1 you can find some instructions on this web page:
http://www.openser.org/dokuwiki/doku.php/install:1.2.2-to-1.3.0
Basically, you will need to implement two steps:
The first one is to create the database using
openserctldbinstead of the oldopenser_mysql.shin Chapter 5.The second one is to use the migrated script 1.3.1 (the script for Chapter 10 migrated to OpenSER 1.3.1).
Version 1.3.x is brand new at the time I'm writing this section. I recommend that you wait a little more time before using 1.3.x in a production environment. The OpenSER development team is releasing a newer version almost every 9 months. It is really hard to cope with their speed. So please check migration instructions if the ones above were insufficient.