[kmeisthax]

Clean room is not the actual requirement for avoiding copyright infringement in reverse engineering. There have been several notable cases in which clean room practices were either not followed or outright disregarded, but the resulting product was considered to be non-infringing anyway[0].

Furthermore, while lots of hard work was put into the code that CoPilot used, that hard work was specifically donated with the intent that the code be reused. The only hard requirement being that the code remain free. The thing people are angry about with CoPilot is that it's a hosted OpenAI product with no freely-available model weights, and that generated code might be regurgitated from training data in some cases[1]. If CoPilot was actually open AI, nobody would be suing over it.

[0] In Sony v. Connectix, it was found that Connectix actually tried clean-room, black-box analysis of the PlayStation ROM, but abandoned it in favor of disassembling the whole thing. Connectix was still ruled non-infringing.

[1] Most egregiously, the comment "evil floating point bit level hacking" will make it spit out Quake III source. Microsoft worked around this by explicitly banning that particular phrase, which is just stupid.