Implementing older version of mySQL on RH9
Personally, I would not risk moving the installed binaries laterally to a newer OS because you may have to drag along needed libraries WHICH MAY NOT WORK IN THE NEWER OS !!!

You should thoroughly look through MySQL's Archives, which goes back to MySQL 5.0.15.

SkySQL also tries to fully accommodate users of older versions of MySQL, MariaDB, and more. Please go to their repository and find the version you need. They go back to MySQL 4.1. 

You should make sure SkySQL has RHEL6 builds, at least.

You could also try compiling MySQL from source within RH9. DISCLAIMER : Never Built MySQL From Source