Last Friday, Automattic founder Matt Mullenweg—the founding developer of the WordPress open source blogging and content management platform—posted an open letter on his personal blog accusing the developers of the blogging site Wix of essentially stealing WordPress code for a new mobile application:

If I were being charitable, I’d say, “The app’s editor is based on the WordPress mobile app’s editor.” If I were being honest, I’d say that Wix copied WordPress without attribution, credit, or following the license. The custom icons, the class names, even the bugs. You can see the forked repositories on GitHub complete with original commits from Alex and Maxime, two developers on Automattic’s mobile team. Wix has always borrowed liberally from WordPress—including their company name, which used to be Wixpress Ltd.—but this blatant rip-off and code theft is beyond anything I’ve seen before from a competitor.

WordPress’ code is open source, but it is published under the GNU Public License (GPL). And the way that Wix used the code, Mullenweg said, is in violation of the GPL. Wix’s new mobile app, he said, reused WordPress’ text editor without credit. And the Wix application was closed and proprietary—not published under the same GPL license.

Wix CEO and co-founder Avishai Abrahami fired back, writing in an open response to Mullenweg, “Wow, dude I did not even know we were fighting.” Abrahami pointed to 224 projects that Wix had open sourced on GitHub, and he admitted that Wix had used the text editor code—making some modifications and sharing the code via GitHub:

Yes, we did use the WordPress open source library for a minor part of the application (that is the concept of open source right?), and everything we improved there or modified, we submitted back as open source, see here in this link – you should check it out, pretty cool way of using it on mobile native. I really think you guys can use it with your app (and it is open source, so you are welcome to use it for free). And, by the way, the part that we used was in fact developed by another and modified by you.

Abrahami was alluding to the use in the WordPress text editor of code originally published as open source under the more permissive MIT public license, as Wix developer Tal Kol said explicitly in a followup post on Medium. Kol said that the code was developed in an attempt to collaborate with WordPress engineers—porting the Automattic, GPL-licensed editor to the React Native JavaScript platform for mobile apps. After a prototype was ready in June, Kol explained, he tweeted a link to the code to Automattic’s engineering team but didn't get a response until October 28, when Mullenweg called Wix out for a GPL violation.

The problem for Wix is that while it may very well have open-sourced the component it built using WordPress’ editor—which Kol says was in turn built using another editor licensed under the more permissive MIT open source license—the company then published the component as part of commercially licensed software. That action violates both the spirit and the letter of the GNU Public License, which requires anything built with GPL-licensed code to be distributed with the same GPL license. By adding the GPL-licensed editor module code to its own application, Wix essentially placed its whole mobile application under the scope of the GPL license.

“I think from what I know, it’s a pretty classic GPL violation,” said Matt Jacobs, vice president and general counsel at Black Duck software, a company that is focused on helping developers get insight into whether code under GPL license or other open source licenses has been incorporated into their code. “So far, it seems to follow a pretty typical line of progression.” When companies incorporate GPL-licensed code into their applications, Jacobs explained, they take on a number of obligations as a result. “One of those obligations is that if you’re going to embed GPL stuff in your code and produce a derivative product, you’re going to have to make that derivative compliant with GPL—either by shipping the code with it or providing the code on request.”

Abrahami’s response that Wix has published lots of its code as open source doesn’t change that fact. “Wix [is] releasing code over here and saying, 'that makes us good guys,'” Jacobs explained. “But the GPL, and the community, doesn’t say if you release enough other code, you’re compliant. They’re dancing around the main issue.”

This is not a rare occurrence. One of the reasons why many companies have avoided GPL-licensed software is the fear of contaminating their intellectual property with GPL-licensed code. But even so, Jacobs told Ars, “Many, many companies are doing this whether they know it or not.”

Kol, Abrahami, and Wix may now be absorbing that lesson. “I know some developers are scared of using GPL, apparently for a pretty good reason,” Kol wrote. Noting that WordPress’ GPL-licensed editor was based on the MIT-licensed ZSSRichTextEditor, he said, “In retrospect, it would have been easier to use it directly.”

Listing image by Jarno Elonen