Apple has decided to offer its Swift 2 programming language as an open source project sometime later this year

Swift 2

During Apple's WWDC 2015 keynote event today, Apple announced that it will offer Swift 2, the next version of its programming language, as an open source project. Standardized open source libraries will be made available for iOS, OS X, and Linux later this year.

Apple also announced that Swift 2 will support whole module optimization, which should makes things faster, along with new error handling. Developers will also be able to see interface "headers:" synthesized in Xcode in Swift 2.