This actually isn't what legal precedent currently says. The precedent is currently looking at actual output, not models being tainted. If you think this is morally wrong, look into getting the laws changed (serious).

What about a human trained on having 30 years of experience working with copyrighted codebases?

Said human would likely not be able to create a clean-room implementation of any of the codebases they worked on.

Judge Alsup -- U.S. District Judge William Alsup said Anthropic made "fair use" of books, deeming it "exceedingly transformative."

"Like any reader aspiring to be a writer, Anthropic's LLMs trained upon works not to race ahead and replicate or supplant them — but to turn a hard corner and create something different"

This quote is both funny and sad. It reads like an advertisement.