[webmaven]

The changes to the editor are released, but the license says that if you incorporate the editor into another peice of software (as Wix has done), the combined work must be released as GPL-licensed source code as well.

There are some narrow exceptions, but Wix's use of the editor component doesn't fall under them.

There is a license that says that you only have to release the changes you make to the component itself, it is called the LGPL, and the Wordpress developers could have used it if that was what they wanted. But they released under the GPL, and Wix should abide by the terms of the GPL, or simply not use the code.