No, I don't believe it is, at least to the extent that the model isn't just copy and pasting code directly.
Creating the model implicates copyright law, that's creating a derivative work. It's probably fair use (transformative, not competing in the market place, etc), but whether or not it is fair use is github's problem and liability, and only if they didn't have a valid license (which they should have for any open source inputs, since they're not distributing the model).
I think the output of the model is just straight up not copyrighted though. A license is a grant of rights, you don't need to be granted rights to use code that is not copyrighted. Remember you don't sue for a license violation (that's not illegal), you sue for copyright infringement. You can't violate a copyright that doesn't exist in the first place.
Sometimes a "license" is interpreted as a contract rather than a license, in which you agreed to terms and conditions to use the code. But that didn't happen here, you didn't agree to terms and conditions, you weren't even told them, there was no meeting of minds, so that can't be held against you. The "worst case" here (which I doubt is the case - since I doubt this AI implicates any contract-like licenses), is that github violated a contract they agreed to, but I don't think that implicates you, you aren't a party to the contract, there was no meeting of minds, you have a code snippet free of copyright received from github...