Considering how ludicrously expensive it would be to even attempt a ground-up retrain (as well as how it might be impossible), weights are enough for 99% of people.
Sharing the end product, but not the tools and resources used to produce it, is how open source has always worked. If I develop software for a commercial operating system using a commercial toolchain, and distribute the source code under GPL, we would call that software open source. Others who get the code don't automatically get the ability to develop it themselves, but that's kind of beside the point. I don't have the rights to publicly redistribute those tools, anyway; the only part I can put under an open source license is the part for which I have copyright.
Training data for a LLM like Llama works similarly when it comes to copyright law. They don't own copyright and/or redistribution rights for all of it, so they can't make it open, even if they want to.
If that seems unsatisfying, that's because it is. Unfortunately, though, I don't think the Free Software community is going to get very far by continuing to try to fight today's openness and digital sovereignty battles using tactics and doctrine that were developed in the 20th century.