The Yahoo iOSSDK is open source to developers in source and binary forms with the freedome to apply modification so far as several terms and conditions are met. The Yahoo pluggin is fully applicable to Xcode and it is required you sign up for a new application ID to get your OAuth consumer key before application.
Mantle makes it easy to write a simple model layer for your Cocoa or Cocoa Touch application. Mantle can still be a convenient translation layer between the API and your managed model objects if you looking to use core data in your application.
Godzippa library is no longer being maintained as of iOS13+ and macOS 10.15+, as the Foundation provides equivalent functionality through APIs like compressed(using:) and decompressed(using:). Godzippa regardless is still available to developers and can easily be implemented via its repo.
webrtc (build scripts) is a set of build scripts useful for building WebRTC libraries for Android and iOS. webrtc (build scripts) scripts can work on most distros, and comes with a well documented READ.me file to better elaborate on implementation.
Aspects is a delightful, simple library for aspect oriented programming by @steipete. Aspects allows you to add code to existing methods per class or per instance, whilst thinking of the insertion point e.g. before/instead/after. Aspects automatically deals with calling super and is easier to use than regular method swizzling.
TBXML is a light-weight XML document parser written in Objective-C and designed for use on Apple iPad, iPhone & iPod Touch and Mac OS devices. TBXML aims to provide the fastest possible XML parsing whilst utilising the fewest resources with this being achieved at the expense of XML validation and modification.
FormatterKit is a collection of well-crafted NSFormatter subclasses for things like units of information, distance, and relative time intervals. Each formatter simplifies the business logic of each domain, so that developers focus on the more important aspects of their applications.