Well, most companies never distribute their models. So GPL doesn't kick in.
I think that the claim that they make is that once a model is "contaminated" with GPL code, every output it ever produces should be considered derived from GPL code, therefore GPL-licensed as well.
alt Hacker News
I think that the claim that they make is that once a model is "contaminated" with GPL code, every output it ever produces should be considered derived from GPL code, therefore GPL-licensed as well.