He should credit author at least. That would be more with the spirit of OpenSource. Not using licences as a defence that "it's legally okay". It is, many things are legally okay, but still a shitty thing to do.
It's NOT legally OK. The license permits use of the copyrighted work with certain terms, attribution being one. That term was violated, just as when a big company takes a low level gpl driver and uses it without releasing the source. AI could have rightly been subject to a DMCA takedown, which is a legal action, for example.
