There are absolutely fully open source models. These are not frontier models, but they very much do exist. OLMo is one of the models explicitly mentioned as having passed the OSI's validation phase. Pythia was also validated by the OSI as meeting its requirements for an open-source AI system. Lucie-7B is a multilingual model is one of the first LLM compliant with the OSI AI definition. Its creators explicitly state that the training dataset, data preparation code, and model weights are all publicly available under open licenses.