AI can rewrite open source code—but can it rewrite the license, too?

Computer engineers and programmers have long relied on reverse engineering as a way to copy the functionality of a computer program without copying that program’s copyright-protected code directly. Now, AI coding tools are raising new issues with how that “clean room” rewrite process plays out both legally, ethically, and practically.

Those issues came to the forefront last week with the release of a new version of chardet, a popular open source python library for automatically detecting character encoding. The repository was originally written by coder Mark Pilgrim in 2006 and released under an LGPL license that placed strict limits on how it could be reused and redistributed.

Dan Blanchard took over maintenance of the repository in 2012 but waded into some controversy with the release of version 7.0 of chardet last week. Blanchard described that overhaul as “a ground-up, MIT-licensed rewrite” of the entire library built with the help of Claude Code to be “much faster and more accurate” than what came before.

Speaking to The Register, Blanchard said that he has long wanted to get chardet added to the Python standard library but that he didn’t have the time to fix problems with “its license, its speed, and its accuracy” that were getting in the way of that goal. With the help of Claude Code, though, Blanchard said he was able to overhaul the library “in roughly five days” and get a 48x performance boost to boot.

Not everyone has been happy with that outcome, though. A poster using the name Mark Pilgrim surfaced on GitHub to argue that this new version amounts to an illegitimate relicensing of Pilgrim’s original code under a more permissive MIT license (which, among other things, allows for its use in closed-source projects). As a modification of his original LGPL-licensed code, Pilgrim argues this new version of chardet must also maintain the same LGPL license.