GNU GRUB is a multiboot boot loader. It was derived from GRUB, the GRand Unified Bootloader, which was originally designed and implemented by Erich Stefan Boleyn. This port does not install GRUB on the master boot record of your hard drive. To do this you will need to read the info page that is installed by the port. This port includes additional patches and fixes making it work properly with ZFS boot-environments.