I don't know about ML specifically, but I've seen a number of projects where people publish supposedly "the source" for something and it doesn't actually build. IMO if they're doing it wilfully that makes not open source, whereas if it's just good-faith legitimate incompetence then it can be.

(My litmus test would be: are they giving you all the stuff they'd give to a new hire/assistant working with them? If they've got a "how to build" on their internal wiki with a bunch of steps they're keeping secret, then it's not open-source. But if the process for a new hire is to hand over a code dump and say "huh, it works on my machine, I don't remember what I did to set it up", then at that point I'd consider it open source. I think this aligns with the "preferred form for making modifications" idea in the licenses).

> But more likely is doing tuning, reinforcement learning, or using a LoRA. Even the company engineers would look at those routes before they looked at retraining from scratch.

Sure. But they'd have that capability in their back pocket for if they needed it. It's a similar story for e.g. parts of the Linux kernel code that are generated via a perl script based on the architecture documentation - you only actually re-run that perl script once in a blue moon, but it's important that they publish the perl script and not just the C that was generated by it.