Mostly Chinese companies that aren't necessarily required to generate infinitely compounding profits just to continue existing.

Edit: Also third parties such as volunteers who fine tune models for specific purposes. Just like with all software - everyone can learn and contribute when it's open source.

They're easily reproducible as copying and pasting. Then given you have a good enough graphics card you can just run it on your local pc completely offline.

Many groups are making models now. I see a future where we have open source data sources, models, and weights. Niche groups can extend models to be trained on whatever they want.