Kubuntu 14.04.3 Amd64 DVD, the new download media does not represent a separate new release, rather it provides fresh installation media with up to date packages and bug fixes.

About Kubuntu
Kubuntu is a free, user-friendly Linux distribution based on KDE's desktop software and on the Ubuntu operating system. It has a biannual release cycle. Besides providing an up-to-date version of the KDE desktop at the time of the release, the project also releases updated KDE packages throughout the lifetime of each release.