In the summer of 2016, after hosting his Stargate server for a while, Xalos decided to openly release the Stargate add-on to the public. (you can find it in here)
Since then though, he has applied numerous bug fixes to his own copy of the add-on and has hosted his Stargate server throughout the years, but hasn't re-released it. I'm aiming to fix some prevalent bugs and also refactor some of the code and add new features that should help new players and make them less confused. Xalos was also going to make a Tutorial for the Stargate gamemode, but he hasn't made it, so I'll try to do that in the future as well.