For reasons of stability, security, and practicality, we do not use the latest release version of MySQL. We are also limited by the latest version of these programs that is compatible with HSPC (for VPS-based accounts) or Plesk (shared hosting accounts).
Each major version (3.x, 4.x, 5.x) of MySQL is a on a different development tree, each of which is maintained separately. MySQL version 3.23.x is extremely stable, and is periodically updated with security patches. The Red Hat Fedora Core 1, 2, and 3 distributions include MySQL 3.23.58 rather than a 4.x or 5.x version. The Red Hat Fedora Core 4 distribution includes MySQL 4.1.
For VPS hosting accounts, we recommend using the version of MySQL that is included as an application template with HSPC unless you know for sure there are features that you have to use in a later version that are not available the default version. If you need a newer version of MySQL, we recommend installing it in a separate location and run it concurrently with your default version of MySQL. You would also need to specifically configure the newer version of MySQL to use different ports than the default version.