> generally you would want people to seed back what they downloaded at least

But the goal is preservation rather than sharing.

I'm confused about how the economics of that would work. If I wanted to contribute to this, I'd have to download the models, so I'd immediately be in the red, and then I could never get out of it because who's going to download these obsolete models? There's no download demand for them; if they were, the whole project would not be necessary.