Kernel-based Virtual Machine (KVM) is a virtualization infrastructure for the Linux kernel that turns it into a hypervisor. It was merged into the Linux kernel mainline in kernel version 2.6.20.
License: Open Source
Citrix XenServer is a commercial virtualization platform offering advanced management and security features, ideal for enterprise environments, while KVM is an open-source solution that provides flexibility and is well-suited for Linux-based environments.