Looks like this has been around for a while now, are there any interesting projects using it?

Edit: https://github.com/SuperSonicHub1/awesome-libsm64

Any demo videos? or just need to imagine it?

found this: https://youtu.be/NXpOCfg8O64

So let me get this straight, is the intent of this so that if you have some game like Call of Duty, you could use this to just add Mario running around in there jumping around like it was SM64?

This is one of my favorite libraries from the premise alone. Here is an example of Mario in Half-Life 2: https://www.youtube.com/watch?v=Ld3qhqkegNw