4MLinux 8.1 (and later) supports a fully automatic installation of the vanilla version of Oracle VirtualBox. This is one of so called "downloadable extensions" (i.e. optional software in 4MLinux, which is installed in the /opt directory by default).
1) Select VirtualBox from the Extensions menu:
2) 4MLinux will download and install VirtualBox for you:
3) Time to configure your new application: