Wine - Open Source Software for running Windows applications on other operating systems.
CodeWeavers CrossOver - Don't buy a Windows license, don't reboot and don't use a Virtual Machine. Try a free trial of CrossOver to run your Windows software on Mac, Linux and Chrome OS.
Lutris - Lutris is an open source gaming platform for GNU/Linux.
Darling - Run macOS applications on Linux
QEMU - QEMU (short for "Quick EMUlator") is a free and open-source hosted hypervisor that...
PlayOnLinux - PlayOnLinux will allow you to play your favorite games on Linux easily