Possible bug, as its readily exploitable -- I noticed the AI I had been steamrolling still showed on the diplomacy screen after snubbing a surrender by surrendering to its own ally instead of me.  I decided to see if I could -- and yes, I could exploit this.  Yes, I was able to negotiate a peace deal with the defeated AI and, through adding in my own techs to offering peace (I am a bit behind technologically in this game -- usually I'm not, but trying out Drengin and the war path thing), was able to get every AI tech and credit in the mix.

Its a completely bogus deal, of course -- the AI will cease to be next turn.  I don't know whether the techs I sold them will get turned over to their ally they surrendered to, but it wouldn't be that much of a loss if it did considering how far behind I am technologically.