Definitions are determined by actual usage. If people call Llama 2’s license open source then ipso facto it’s open source.
See! Actual usage! The sky is now green.
The only reason people say that Llama 2 is open source is because they have been misled, not because the definition is changing. There's a lot of goodwill around the term "open source" because of its actual meaning, so it will always be tempting to abuse it for your own benefit, as not everyone bothers to check whether your claims are actually true.