> AFAIK, they were the first open everything model.

GPT2 (released ~5 years ago?) was "open" in the sense that weights were available for download (sans license), exact datasets that were used where outlined, the architecture explained and so on, so I guess it was also "open" in the sense that Llama is "open", but neither would be "open source" which I'd feel pretty confident to label OLMo with.

So OLMo seems to be the first actually "open source" model, but maybe not "open" as in "downloadable" (which Facebook tries to call "open source").