The GNU Boot project issued their December 2023 news update and shared that they have issued a new release candidate in working towards GNU Boot 0.1. They also realized they had included some non-free software within the source release of GNU Boot. Their monthly news update explains:
"In the GNU Boot source release (gnuboot-0.1-rc1_src.tar.xz) we found the 3 files (F12MicrocodePatch03000002.c, F12MicrocodePatch0300000e.c, F12MicrocodePatch03000027.c) that contain microcode in binary form, without corresponding source code. GNU Boot 0.1 RC1 corresponding source code tarball was remade without these files (and renamed). The images for the Asus KCMA-D8, KFSN4-DRE and KGPE-D16 were also removed as they may contain the nonfree code as well. The rest of the files are unaffected."
Those microcode patch source files are for Those microcode C files removed are for AMD Family 12 microcode patches that were distributed as part of the open-source AMD AGESA code from a decade ago. The C files are arrays of ROM data for applying CPU microcode updates. But as it's not original open-source code itself and effectively a binary blob, GNU Boot is dropping those microcode updates in the name of free software.
The motherboard ports removed ASUS KCMA-D8, ASUS KFSN4-DRE, and ASUS KGPE-D16 are for old AMD Opteron server motherboards. Some of these AMD Opteron motherboards remain popular with open-source enthusiasts for the ability to easily run Coreboot/Libreboot and formerly GNU Boot on them, even though by today's standards they are woefully outdated in features, performance, and power efficiency.