So far we've seen PS4 PUP Unpackers, PS4 PKG Scripts, official Sony PS4 PKG / SDK Tools leaked, homebrew PS4Dev Tools and now PlayStation 4 developer Keyaku shared his PS4 PKG unpacking tools with the scene!
My collection of tools for PS4 file handling.
flat_z (original Python scripts for PUP and PKG unpacking)
pupunpack: splits PS4UPDATE.PUP and exposes inner PUP files (encrypted).
unpkg: unpacks retail/debug PKG files while collecting data and dumping internal files (mostly a C port of flat_z's Python script, at the moment).
PSDEV Wiki: http://www.psdevwiki.com/ps4/Talk:PKG_files