Relicensing with AI-Assisted Rewrite

How do you do phase 2 with an LLM when the LLM is likely trained on the original source code? Isn't this equivalent of "rewriting" Harry Potter by describing the plot to an LLM trained on the original books[1]?

[1] https://arstechnica.com/features/2025/06/study-metas-llama-3...

The worst problem is that a LLM could not only copy the exact code it was trained on but possibly even their comments!

There is one thing arguing that the code is a one to one copy but when the comments are even the same isn’t it quite clear it’s a copy?

> it sounds like some legal jester dance done to entertain [...] copyright laws

Clean room implementations are a jester dance around the judiciary. The whole point is to avoid legal ambiguity.

You are not required to do this by law, you are doing this voluntarily to make potential legal arguments easier.

The alternative is going over the whole codebase in question and arguing basically line by line whether things are derivative or not in front of a judge (which is a lot of work for everyone involved, subjective, and uncertain!).

It literally did copy significant portions of docstring comments, verbatim.

> If you had a hermetically sealed code base that just happened to coincide line for line with the codebase for GCC, it would still be a copy.

If you somehow actually randomly produce the same code without a reference, it's not a copy and doesn't violate copyright. You're going to get sued and lose, but platonically, you're in the clear. If it's merely somewhat similar, then you're probably in the clear in practice too: it gets very easy very fast to argue that the similarities are structural consequences of the uncopyrightable parts of the functionality.

> The actual meaning of a "clean room implementation" is that it is derived from an API and not from an implementation (I am simplifying slightly).

This is almost the opposite of correct. A clean room implementation's dirty phase produces a specification that is allowed to include uncopyrightable implementation details. It is NOT defined as producing an API, and if you produce an API spec that matches the original too closely, you might have just dirtied your process by including copyrightable parts of the shape of the API in the spec. Google vs Oracle made this more annoying than it used to be.

> Whether the reimplementation is actually a "new implementation" is a subjective but empirical question that basically hinges on how similar the new codebase is to the old one. If it's too similar, it's a copy.

If you follow CRRE, it's not a copy, full stop, even if it's somehow 1:1 identical. It's going to be JUDGED as a copy, because substantial similarity for nontrivial amounts of code means that you almost certainly stepped outside of the clean room process and it no longer functions as a defense, but if you did follow CRRE, then it's platonically not a copy.

> What the chardet maintainers have done here is legally very irresponsible.

I agree with this, but it's probably not as dramatic as you think it is. There was an issue with a free Japanese font/typeface a decade or two ago that was accused of mechanically (rather than manually) copying the outlines of a commercial Japanese font. Typeface outlines aren't copyrightable in the US or Japan, but they are in some parts of Europe, and the exact structure of a given font is copyrightable everywhere (e.g. the vector data or bitmap field for a digital typeface, as opposed to the idea of its shape). What was the outcome of this problem? Distros stopped shipping the font and replaced it with something vaguely compatible. Was the font actually infringing? Probably not, but better safe than sorry.