It is loaded from a FAT16 or FAT32 filesystem on removeable media, the hardware does not accommodate loading it from a ROM. This includes software that runs on the VideoCore part of the Broadcom SoCs which boots the arm cores and continues to provide services to the arm cores after they have booted. Redistribution is permitted subject to the conditions outlined in https://github.com/raspberrypi/firmware/blob/master/boot/LICENCE.broadcom feedback from and ok sthen@ ok phessler@ on an earlier version.