Don't know about the signing aspect, but I know that Danny at least confirmed that they're under negotiations for him as a player.
As for the teammate aspect, let's play the other side of it. Do you have concrete statements or evidence that his big mouth causes trouble in the locker room? Makes no sense to me to start assuming stuff about people and their relationships.
I know that Rondo has complemented Sam quite a few times for his "teachings". Doc has complemented Sam quite a few times for teaching his young pointguards saying stuff like "Sam is quite valuable because it allows me to spend less time worrying and coaching the young pointguards and I can focus on other aspects of the game". Paul Pierce attributed some of his playoff success, especially the big game against LeBron, to some drills and practices he did with Sam. Garnett has been a teammate of his in the past, and he played a big role in bringing him last year. Heck, Sam even stayed with him. With the Clippers, you'd often see the players going towards Sam for directions instead of the coach.