That doesn't change the meaning of Open Source. These are "free as in beer", not "free as in [modify the sources and rebuild it]". There are LLMs for which that is true, which include a specific list of training data. If you wanted to "uncensor" one of those, you could curate the source data and rebuild it, instead of trying to get it to unlearn what it was taught.

If you had petabytes of highly interconnected source code, it could.

In a rough way, a NN is just a compiler designed to translate a boatload of simple data into a useful program that operates on similar data.

Yea the weights are the secret sauce that OpenAI and competitors generally protect.