Previewed at WWDC, launching in the fall.
Apple's Swift Programming Language Now Open Source
We are excited by this new chapter in the story of Swift. After Apple unveiled the Swift programming language, it quickly became one of the fastest growing languages in history. Swift makes it easy to write software that is incredibly fast and safe by design. Now that Swift is open source, you can help make the best general purpose programming language available everywhere.Announced at WWDC 2014 and launched alongside iOS 8 and OS X Yosemite a few months later, Swift marks a significant step forward from the Objective-C previously favored by Apple.
On December 3, 2015, the Swift language, supporting libraries, debugger, and package manager were published under the Apache 2.0 license with a Runtime Library Exception, and Swift.org was created to host the project. The source code is hosted on GitHub where it is easy for anyone to get the code, build it themselves, and even create pull requests to contribute code back to the project. Everyone is welcome, even just to file a bug report. There are excellent Getting Started guides available here on the site as well.With the open sourcing of Swift, Apple has also released a Linux port to expand access to the language. Apple has also begun sharing design guidelines related to the upcoming Swift 3, setting the stage for "a more cohesive feel to Swift development."
The project is governed by a core team of engineers that drive the strategic direction by working with the community, and a collection of code owners responsible for the day-to-day project management. Technical leaders come from the community of contributors and anyone can earn the right to lead an area of Swift. The Community Guidelines includes detailed information on how the Swift community is managed.
Update: Apple has published a press release announcing the news and Apple's Senior VP of Software Engineering, Craig Federighi, has done an interview with Ars Technica on Apple's decision to make Swift open source.