I agree with you to the extent that yeah technically it's not open source because the data is not known. But for these foundation models like Llama, the model s

I agree with you to the extent that yeah technically it's not open source because the data is not known. But for these foundation models like Llama, the model structure is obviously known, pretty sure (didn't check) the hyperparameters used to train the model is known, the remaining unknown of data, it's pretty much the same for all foundation models, CommonCrawl etc. So replicating Llama once you know all that is a mechanical step and so isn't really closed source in a sense. Though probably some new term open something is more appropriate. The real sauce is the data you fine tune these foundation models on, so RLHF, specific proprietary data for your subfield, etc. The model definition, basically Transformer architecture and a bunch of tricks to get it to scale are mostly all published material, hyper parameters to train the model are less accessible but also part of published literature; then the data and (probably) niche field you apply it to becomes the key. Gonna be fun times!