Simon WillisonMar 5
The chardet open source library relicensed from LGPL to MIT two days ago thanks to a Claude Code assisted "clean room" rewrite - but original author Mark Pilgrim is disputing that the way this was done justifies the change in license - my notes here: https://simonwillison.net/2026/Mar/5/chardet/
Can coding agents relicense open source through a “clean room” implementation of code?

Over the past few months it’s become clear that coding agents are extraordinarily good at building a weird version of a “clean room” implementation of code. The most famous version …

Simon Willison’s Weblog
Show threadmnmlst
@simon the argument this is not derivative leans heavily in the determination from JPLag and its self-proclaimed state of the art. This exemplifies again how plagiarism detection tools are falling behind in the red queen race of AI.
Mar 5 at 8:46pmWeb
Show threadMagnus AhltorpMar 9

@mnmlst @simon Working around a specific offline-runnable plagiarism tool naively seems trivial by simply training an obfuscation system on the score.

Compare how easy it was to fool earlier ROUGE text summarisation scores:

https://www.dr-hato.se/research/abuserouge.pdf