VirtualBox is a full virtualizer available on macOS, Windows, and Linux. When you install an operating system in VirtualBox, you're not dual-booting the new OS alongside the original one.

In order to make this work, a workaround is employed, which uses the fossilized Mac-on-Linux project to run PowerPC Mac OS essentially on Linux for the Wii.

Installing OS X on older Macs This web page offers instructions on how to install Mac OS X 10.0 on the 7300 - 9600 series Macs, and possibly some other models. It also has a link to the author's ...