Apple's example code license:
https://developer.apple.com/su...
It appears there are basically two conditions:
1) if you distribute the thing unmodified you include the license text
2) you don't blame Apple for whatever happens, and if you're modifying it you don't stamp their name on it.
The fact that they're licensing the model weights themselves, and maybe some other stuff useful for training these things, means that you can fine tune, retrain, whatever the model (modify it to your purposes) and then it's yours, you can do whatever you want with it, just as if you'd written your own program based on some freely licensed example code.
Want to rebuild Tay the Nazi chatbot and sell it to white supremacist groups for massive profits? Have fun, just don't stamp Apple's logo on it or blame them for any consequences.