https://medium.com/@talkol/how-i-found-myself-accused-of-ste...
> I know some developers are scared of using GPL, apparently for a pretty good reason. The WordPress GPL Rich Text component in question, is actually a wrapper around another Rich Text component named ZSSRichTextEditor which is licensed MIT. In retrospect it would have been easier to use it directly.
https://github.com/nnhubbard/ZSSRichTextEditor
https://github.com/wordpress-mobile/WordPress-Editor-iOS
So, Wix built a wrapper for a GPL piece of code, which was just a wrapper for a MIT piece of code. According to this tweet[0], the only thing Wix needs to do is to assign a GPL license to their code...but alas IANAL.
[0] - https://twitter.com/nitrogen/status/792486850845773824
EDIT - From the OP's blog:
> When you embed and use GPL code, you have to release the entire thing as GPL. (That’s why it’s called a viral license.) So they need to release not just their changes to the editor, but the entire app that was distributed.