If you look at that repo, what they are doing is totally unambiguous. The README literally acknowledges that they are using Wordpress code, describing the contents of the repository as a "React Native Wrapper for WordPress Rich Text Editor."
They applied the MIT license to their wrapper, which is using the GPL-licensed Wordpress code, and then they embed the whole thing in their proprietary app. They are now compelled to publish the source code of their entire application if they want to comply with the requirements of the GPL.
Comments
Matt links to the relevant GitHub repo in his blog post: https://github.com/wix/react-native-wordpress-editor
If you look at that repo, what they are doing is totally unambiguous. The README literally acknowledges that they are using Wordpress code, describing the contents of the repository as a "React Native Wrapper for WordPress Rich Text Editor."
They applied the MIT license to their wrapper, which is using the GPL-licensed Wordpress code, and then they embed the whole thing in their proprietary app. They are now compelled to publish the source code of their entire application if they want to comply with the requirements of the GPL.
If they don't distribute it (SaaS only) then they do not need to publish anything.
That's not necessarily true. Some licenses consider html itself as protected code.
It's an iOS application. They are distributing it in the iOS App Store.