This seems to ignore the widely repeated claim that GitHub's terms of service explicitly grant them a license beyond the actual open source license attached to the code and thus transfer the burden of liability to the uploader when it comes to code they can not control the licensing of.
So either this is about code authored by people who did not use GitHub (in which case GitHub would be immediately liable, though they could try to sue whoever uploaded that code to GitHub for damages) or it's going to have to argue that the terms of service can't smuggle in a provision that effectively sidesteps even the most permissive open source licenses.
The relevant part of the terms would be https://docs.github.com/en/site-policy/github-terms/github-t..., plus the definition of Service, which would include Copilot. I don’t believe GitHub have ever claimed to be or suggested that they are using this, and I think it would be a very shaky claim in a court due to the second paragraph.
Rather, GitHub have consistently cited “fair use”, as also noted in the suit, including in the summary at https://unicourt.com/case/pc-db5-doe-1-et-al-v-github-inc-et.... I also don’t believe GitHub have ever claimed to only use GitHub repositories, though I know of no obvious evidence of them having fetched from other sources, and they may well not have simply because it’s more convenient not to and they’ve got enough already, even if it honestly weakens their position (“if you’re relying on ‘fair use’, why haven’t you added closed-source software like the GitHub backend to show you mean it?”).
I think they're challenging the validity of what's in the user license agreement. Companies can put whatever they want in there, but not everything is enforceable.
I think it wouldn't be enforceable in a consumer service (at least in my jurisdiction, see a German court ruling against WhatsApp banning a user for using a third-party client by claiming doing so violated their ToS).
But given that implicitly or explicitly GitHub users act more like users of a commercial service (remember: commercial doesn't mean paid or b2b), things might be different given that consumer protections don't necessarily apply.
Personally I'd love to see the same "you can't hide surprises in your ToS to obtain 'consent'" yardstick be applied here though, commercial service or not.
Is the actual complaint linked or quoted somewhere in the article? I've re-read it twice and it spends most of its wordcount explaining what open source is, mentioning a previous case and describing the implications of the attribution requirement with regard to the DMCA. There are plenty of links but they go in all kinds of places except to the ruling itself.
Your response is not very helpful beyond telling me I lack information I'm unaware of and couldn't find.
So either this is about code authored by people who did not use GitHub (in which case GitHub would be immediately liable, though they could try to sue whoever uploaded that code to GitHub for damages) or it's going to have to argue that the terms of service can't smuggle in a provision that effectively sidesteps even the most permissive open source licenses.