I'm actually right maybe you should do a little bit more research on the subject. Brancato and Ferris are credited for writing the script and I'm aware that Haggis,Nolan,Zuckier, and Ryan all worked on rewrites but the initial script was written by those two and they are the ones receiving credit for the writing. Obviously those re-writes didn't help much.
Plus the majority of the script still contains most of Brancato and Ferris original story thus them receiving credit and Nolan and Haggis receiving none.
Dig deeper. McG has been quoted several times saying the BULK of the script was re-written by Nolan. The fact that Nolan was not credited has nothing to do with how much work he did on the script. The Brancato and Ferris script had Marcus as the main character in the story and the script was about the journey Marcus takes. Obviously this is not what Salvation is about. Nolan and the others who helped rewrite it made John the main character instead of Marcus, and also put more focus on Skynet as well as the creation of the T-800. The whole T-800 sub-plot barely even existed in the original Brancato and Ferris draft.
Also the fact remains that Bale wanted NOTHING to do with the movie when he read the Brancato and Ferris original draft, so obviously the rewrites DID help, enough to convince Bale to do the movie.
. If you don't want to believe the facts, that is your perogative. Jonah Nolan by the way confirmed himself he worked on the script. 