On Friday, October 28, WordPress’s co-creator Matt Mullenweg accused Wix of a "blatant rip-off and code theft". Wix had just released Wix App. It lets users manage their websites and Wix operating systems from their mobile devices. The app includes various functionalities ranging from managing a Wix online store to letting one edit her Wix blog posts. It is the Wix App’s Rich Text Editor that sparked the turmoil. Mullenweg contends that it is based on the WordPress mobile app’s editor. In a heated discussion with Wix's CEO, Mullenweg asserted that "it doesn’t matter if it’s 30 lines or 30 million lines: because it includes GPL code and you distributed the app, the entire thing needs to be GPL."
Wix CEO, Avishai Abrahami, admitted using the WordPress open source library "for a minor part of the application (that is the concept of open source right?)" and emphasized that Wix published back the open source repository on GitHub everything they improved or modified. Abrahami stated that Wix already published 224 open source projects and contributed numerous bug fixed to other projects. He further promised that "we will release the app you saw as well".
So it seems that it all boils down to this: Wix included a WordPress library within its App. The library is subject to the GPL. Does that make the whole App subject to the General Public License? WordPress is licensed under GPL v. 2 or any later version. The GPL is a strong reciprocity license. When one redistributes a GPL’d program, the GPL requires to make the program’s source code available to third parties. If the original GPL’d program is modified, the developer must make her modification available to third parties. One of the primary and often onerous requirements of the GPL, is that any software that is based on the GPL’d component - "that is to say, a work containing the Program or a portion of it, either verbatim or with modifications" - must be distributed under the GPL.
So how far into the code can the GPL reach? What constitutes code that is based on a GPL component is highly debatable. For instance, does dynamically linking proprietary code with a GPL’d component result in an overall program that is considered to be “based on the GPL’d component”? The answer depends on whom you ask. Prominent figures in the Free Software community may disagree. For example, Richard Stallman, the father-figure of Free Software and the drafter of the first GPLs, advocates a very wide interpretation of the license's provisions. On the other hand, Lawrence Rosen, formerly legal counsel of the Open Source Initiative (OSI) takes a more reserved approach ("Dynamic linking… is a transitory relationship between two programs for which they are each pre-designed… Such linkage does not constitute the creation of a derivative work". The Unreasonable Fear of Infection). One article that discusses the dispute is titled Software Combinations as Derivative Works under Copyright Law and GPL. While it dates back to 2006, nothing has really changed since its publication. There were no judicial precedents on this point 10 years ago, and there are still none today.
All parties seem to agree, though, that statically linking of GPL component with proprietary code creates a derivative work and hence subjects the proprietary code to the GPL.
It may be that WordPress and Wix took different approaches: WordPress advocates the more-prevalent opinion in the Open Source Software community – "if a piece of software includes any components from other GPL software, that makes the whole new piece of software GPL and it should therefore be made public if distributed" (Miriam Schwab, CEO of illumine at WPGarage). While they do not elaborate on the legal aspects of the dispute, Wix may be taking a different approach: The Wix App as a whole is not based on WP's editor. And If the Rich Text Editor was wraped in order to adjust it to React Native, the wrapper may effectively separate the original GPL code from the proprietary Wix code. Such approach may be valid as long as the Editor's code is not statically linked against Wix's proprietary code.
In their latest posts, WordPress toned down their statements, maybe because Wix promised to release the source code of their App. In order to follow the GPL, Wix will have to take further steps such as providing copies of the GPL license text along with their distribution, keeping intact any notices already present at the WordPress library that address the licenses or the absence of warranty, causing the modified files to carry prominent notices stating that Wix changed the files and the date of any change etc.
Miriam Schwab suggested in her post that "If you are a commercial company, think a bajillion times before using Open Source code in your proprietary software". This kind of statements thickens the fear that some companies have about using Open Source. The truth of the matter is that Open Source may be used safely in almost every cases as long as the developer is aware of the license terms, controls the use and follows the license provisions. This is no doubt demanding, but not unfeasible.