Is it a Unity app exported to HTML5 (w JS and WebGL)?
Seems so.
But the rest of it is Three.JS. Thus were the assets created in Unity and someone copied the shader code to ensure that they render the same in ThreeJS as in Unity? I am a little confused.
Btw there is proprietary/coprighted unity shader code cut and pasted into this, someobe even copied the original comments from the unity shaders. For example search for "DecodeLightmapRGBM" in the below source code, which is from the demo - that code and others are copied:
https://gist.github.com/bhouston/1c3c6835ca9766571f07ad0126d...
Here is some unity source code to compare against: https://gist.github.com/nicloay/8d2ae254a77de58bb42b9009b4cf...