The Swift Foundation framework is moving to open source.

The team wants to open up not only the language itself, but also the ecosystem around it.  The Foundation has played an important role in the success of software for decades and has been an integral part of the Swift developer experience from the beginning.

No more wrapped C code. With Swift Foundation's own implementation, the platform will no longer waste power converting between C and Swift, resulting in better performance. The Swift implementation, developed as a package, also makes it easier for Swift developers to check, understand, and add code.