iTerm2 is a terminal emulator for Mac OS X that does amazing things.

KeyCastr, an open-source keystroke visualizer

Staggeringly powerful macOS desktop automation with Lua

Darwin/macOS emulation layer for Linux

LuLu is the free macOS firewall

Mac app that shows all open files, directories, sockets, pipes and devices in use by all running processes. Nice GUI for lsof.

A fast and clever hex editor for macOS

Mac Mouse Fix - Make Your $10 Mouse Better Than an Apple Trackpad!

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Quicksilver Project Source

Control the fans of every Intel Mac to make it run cooler

BlockBlock provides continual protection by monitoring persistence locations.

MobileOrg iPhone App

Process Monitor Library (based on Apple's new Endpoint Security Framework)

Enumerate persistently installed software

Malware and other applications may install persistent keyboard "event taps" to intercept your keystrokes. ReiKey can scan, detect, and monitor for such taps!

Command line tool for getting and setting a default browser (HTTP handler) in macOS

macOS comic viewer

Gomobile support for Age