Wow that's hot. I was not aware that you need to be "untainted" by the original LGPL code. This could mean that...

All AI generated code is tainted with GPL/LGPL because the LLMs might have been taught with it

Being completely untainted is the standard many reimplementations set for themselves to completely rule out legal trouble. For example ReactOS won't let you contribute if you have ever seen Windows code. Because if you have never seen it, there can be no allegation that you copied it.

That is however stricter than what's actually legally necessary. It's just that the actual legal standard would require a court ruling to determine if you passed it, and everyone wants to avoid that. As a consequence there also aren't a lot of court cases to draw similarities to

"Taint" requires that the code is demonstratably derivative from the *GPL licensed work.

This is actually harder standard than some people think.

The absolute clean room approaches in USA are there because they help short circuit a long lawsuit where a bigger corp can drag forever until you're broken.

Not a lawyer, but that always seemed naively correct to me.

However, the copyright system has always be a sham to protect US capital interests. So I would be very surprised if this is actually ruled/enforced. And in any case american legislators can just change the law.

Yes, that's what some lonely people have been shouting in the desert since the LLM craze started.