The blog post acknowledges that the inspiration for the app was the Apple site (and a post on HN). None of the code is shared with their implementation (and all

The blog post acknowledges that the inspiration for the app was the Apple site (and a post on HN). None of the code is shared with their implementation (and all Phosphor's javascript is under MIT license, https://github.com/mikewoodworth/phosphorframework https://github.com/mikewoodworth/phosphorframework), and the Phosphor encoder itself is far more space-efficient than whatever toolset Apple is using internally.