They don't have a weird definition of open source. I recently outlined a LLM chat that I think clearly outlines this: https://news.ycombinator.com/item?id=40035688
The LLM equivalent here would be programmatically generating synthetic input or cleaning input for training. You don't need the tools used to generate or clean the data in order to train the model, and thus they can be propriety in the context of an open source model, so long as the source for the model is open (the training data).
No, the same way training is not a build dependency for the weights source code. You can literally compile and run them without any training data.
You mean the same source code? Because... I agree. That's why it's important for the source to be open. Both in the context of software and language models.