not (just) grub, no. it's a new gnu project, still release candidate, a distribution of boot firmware for motherboards, the stuff that loads the boot loader. the flashable images contain grub though, because it's convenient.
https://gnu.org/s/gnuboot
https://ftp.gnu.org/pub/gnu/gnuboot/

you may have heard of GNU Libreboot before. it used to be free software, but it left GNU and then forked things up to embrace, expand and enable binary blobs to take away the freedom from its users. GNU boot is the continuation of what Libreboot should have never ceased to be, and thus the deserving recipient of all the praise and recommendation we used to place on Libreboot back when it deserving of that name, before it became Lie-breboot