By "work on", I mean "making direct edits". If we take broad definition of "work on", we lose all the distinction between source code and output. Any binary code is source code in any project, because the programmers simply is using tools to work on them, like the compiler.
For all practical purposes, if you are part of the team who released the LLMs, you would be writing and modifying the code of data processing, of the model, and of the training process. Those should be considered source code.
And we do have the model, which is pretty Oss-y, and which is why we can fine-tune the weights. But from a broader perspective, it's not fully Oss-y, because we don't have the code for anything else. There's no way to change, for example, how the training is done in the first place.
