Kubuntu is an official flavour of the Ubuntu operating system which uses the KDE Plasma Desktop instead of the Unity graphical environment. Developed by Canonical Ltd
License: Open Source
Knoppix is primarily a live distribution focused on providing a robust environment for immediate use without installation, making it great for recovery and troubleshooting. In contrast, Kubuntu is a full-fledged Linux distribution based on Ubuntu, designed for daily use with a stable environment and extensive software options.