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

Staggeringly powerful macOS desktop automation with Lua

Darwin/macOS emulation layer for Linux

Model framework for Cocoa and Cocoa Touch

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

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

Xcode plugin for Vim keybindings

Chameleon is a port of Apple's UIKit for iOS (and some minimal related frameworks) to Mac OS X.

Per-device scrolling prefs on macOS.

Quicksilver Project Source

Source for many of The Omni Group's frameworks

Nu is an interpreted Lisp that builds on the Objective-C runtime and Foundation framework.

A fast, simple graph drawing and data plotting app for OS X and iPad.

IRC Client for Mac

General purpose plain text editor for macOS. Widely known for its live collaboration feature.

NSWindow subclass with a highly customizable title bar and traffic lights

A Mac OS X forensic utility which manages file system mounting in support of forensic procedures.

Small command-line program for OS X that moves files or folders to the trash.

IRCCloud iOS App

Reader for Mac like Animation NSSegmentedControl