Erich Boleyn originally designed and implemented GRUB.

VaX#n8 (real name unknown) wrote shared_src/fsys_ext2fs.c.

Heiko Schroeder rewrote shared_src/stage1.S to be more readable.

Gordon Matzigkeit adopted GRUB into the GNU Project.  He fixed several
bugs, added symbolic link support to shared_src/fsys_ext2fs.c, and
implemented the grub configuration program.