When Apple unveiled Swift 2.0 at WWDC back in June, one of the bigger announcements was that the language would be going open source by the end of the year. The time has come—just a few weeks before its self-imposed deadline, Apple has launched Swift.org and is releasing a big chunk of code (as well as some guidance for Swift 3.0) to the public.
Swift is being released under an Apache 2.0 license, which is incidentally the same license Microsoft used when it open-sourced a big chunk of its .NET framework last year. The project is hosted on GitHub and includes the compiler, the LLDB debugger, the REPL command-line environment, the standard and core libraries, and code from supporting projects. New to Swift (and also open source) is the Swift Package Manager, described as an “early-stage project” that will serve as a repository for Swift modules and will evolve with input from the community.
Apple has also posted information about then next version of Swift. Instead of getting a big Swift 3.0 info dump at WWDC 2016 in the summer and then digging into the Xcode betas and adapting, developers can already find an “evolution" document on the Swift site that maps out where the language is headed in its next major version. One of Apple's major goals for Swift 3.0 is source compatibility, meaning that code written to target Swift 3.0 will continue to compile properly even as the language continues to develop. This isn't true of older Swift versions, and Apple is already warning developers that some things are going to break between Swift 2.x and 3.0.