At the Apple Worldwide Developer Conference (WWDC), Apple announced that they would open source Swift 2.0 and make it available later this year. Swift is the programming language that Apple has been positioning for developing for the Apple platforms, which include OS X and iOS. In their June 8th blog, Apple stated the following regarding the new version of Swift:
"This new version has even better performance, a new error handling API, and first-class support for availability checking. And, platform APIs feel even more natural in Swift with enhancements to the Apple SDKs."
With the release to the OSI-approved permission license, Apple will be accepting contributions to Swift going forward. Equally important, they will be targeting Linux in addition to their existing operating systems. Finally, in addition to Swift being open sourced, the standard libraries and compiler will also be open sourced.
For more around the announcement, check out Darryl Taft's article, Apple Expects Open-Sourcing Swift Language to Boost Adoption.