Sorry for the late reply, I actually had to dig in inside the .xp3 files, to find the song and it's file name.
The origin of the song is from one of the websites listed in the readme called oo39 dot com, the game has many songs from there and the intro is one of them, the only thing I could find aside from that, is that is called "YS174", no artist, or the source of the vocoder voice, or anything unfortunately.
Also, interestingly, there wasn't any need to credit even the song, so I suppose Dendo just wanted to be sure to credit everything.
EDIT: Nevermind, if you don't pay for the "premium" service of that website you need to credit the song, so it's actually free to use too, with obligatory crediting+link I think.