Sadly, Portal64 has come to an end after cease & desist letters were issued to James. Still, it was a fantastic series and he is a great presenter, he makes the technical challenges he faces so Interesting to follow.
Source? All I see is that Valve kindly asked him to take down the project before Nintendo comes after them for using Nintendo's proprietary libraries, but the project could hypothetically continue if he switched to an open source library instead.
Nintendo has yet to do anything but as we've seen from Pokémon mods in the past they like to wait up until release. Dudes got a video on the topic if you want to hear it from his own mouth https://youtu.be/AdBzok8GjA0
It really sucks and i wish i had cloned the repo. To me the code was so clean and easily readable, i wanted to look over it more to learn for my own n64 project.