It just means that tiktok is using a software component that was developed by facebook and that is publicly available for everyone to use.
You want to use it too in a project of yours? You can, but you have to add that license text somewhere!
This doesn't mean that anyone owns anything, open source software is full of these so-called "libraries" that people reuse in order to not reinvent the wheel constantly.
Google translate does that, you can also use it on real-world text with your camera and the translation results look exactly like that