It doesn't, you can download toolchains from swift.org or build them yourselves and load them into your old version of Xcode.

But you're not allowed to submit apps to the stores with unofficial toolchains.

> It doesn't, you can download toolchains from swift.org or build them yourselves and load them into your old version of Xcode.

IIRC, the toolchain checks the versions of SDKs shipped in the installed Xcode and refuse to compile your source code if anything's not up to date.

> But you're not allowed to submit apps to the stores with unofficial toolchains.

Not sure this is true. Apple does not allow you to copy/run Xcode from non-Apple hardware. Other than that, submitting an app built with an OSS toolchain should be fine.

See the note at the bottom: "Apps uploaded to iTunes Connect must be built using the default toolchain."

https://developer.apple.com/library/archive/documentation/To...

Really obviates the supposedly open nature of the language.

Not really. They just require certain compiler builds to ship on their app store.