unpackbootimg, mkbootimg:
https://github.com/CyanogenMod/android_system_core/tree/cm-10.2/mkbootimg/ (inital sources)
https://github.com/huaixzk/unpackbootimg/ (makefiles)
https://github.com/osm0sis/mkbootimg/ (patches)

mkbootfs:
https://github.com/CyanogenMod/android_system_core/tree/cm-11.0/cpio/ (initial source)
https://github.com/trevd/android_system_core_cpio/ (makefile)
https://github.com/osm0sis/mkbootfs/ (patches)

lz4:
http://cyan4973.github.io/lz4/

magic:
http://www.darwinsys.com/file/

gzip, bzip2, lzop, xz; awk, basename, cut, cpio, dirname, file, find, sudo:
(required system packages/commands)

shell scripts:
osm0sis@xda-developers (scripting)
Peteragent5, alansj & iridaki@xda-developers (general method)
