Uncle Jim is an older, friendly man with a grand-fatherly charm who is still useful because of his mechanical skill. He is timid and prefers not to get involved in conflicts. Uncle Jim is one of the traitors, but isn't a bad guy. He is content to remain in Denver, but is torn between loyalty to Porter and the chance of a big steal from the Box. That said, he still spurs on Hardin's unpredictable nature.
Not dealing with the traitor Salvagers before attempting to explore the Box will, in a cut scene, result in a violent conflict as the traitors turn up looking to take it for themselves. If Bombay Jack also wasn't dealt with it will include him detonating the bombs in his base in an attempt to take everyone else out with him. The Prisoner and any companions will be scattered around the rubble alive but severely injured.
If the Prisoner puts off exploring the Box for long enough, the traitor Salvagers will go ahead with their plan to strike it. The Prisoner will hear their interactions over a radio and may be able to get their before the showdown if he is quick. If not, he will reach the Box only to find that Jack was able to snipe or bomb all of them and will already be stripping their corpses, he will already have done this too if the Prisoner puts off investigation even longer.
While Jim is willing to fight as part of a team he is more likely to flee or surrender than take on the Prisoner alone.