Well, the licence tries to prohibit people doing various things with it, but the model is open weights. Anyone can physically run it on their hardware, not something they can do with ChatGPT or Claude for example. You're right, I shouldn't have implied it was fully open source, but at least it only tries to legally, rather than physically, prevent people running and modifying the model themselves.
there is no official/real definition of open source
the definition you probably mean is hillariously silly. There's one project that is pretty big and well-receifed in the community but isn't open source according to them because it contains the paragraph "don't do evil" in its license.
Huh? Open source has a definition. It means the source is accessible and one can build the software themself. I think you might be mixing up open source and FOSS (which does have to do with licenses).