https://www.merriam-webster.com/dictionary/open-source
Perhaps you are right and this LLM-specific usage enters a dictionary at some point.
As I believe it is very misleading, I am doing my part to discourage it — it is not, imho, impolite to point out established meaning of words when people misuse them. We all create a language together, and all sides have their say.
I think the debate has been around what constitutes the source code. The mode has settled on weights. The spirit of the dictionary definition seems fine for excluding a definition that’s only practical if you own a multimillion-dollar ersatz mainframe.