questions...

1) How could one connect to the internet through the collective memory of deceased people?

2) If the Source Code simulation was made from the collective memory of the deceased passengers, how was Colter Stevens able to interact with Derek Frost as he wasn't among the victims on the train?
Sure other passengers might have memory images of Derek but they wouldn't have any memory of the the van, it's license plate and the bomb within.
Sure his wallet was on the train... but the information within would be unknown to the passengers if they had no memory of seeing the information.

3) How could Colter Stevens talk to his dad from within the simulation?
I don't see any other way of interpreting this than being his own imagination in the afterlife.

However you look at it, the Source Code simulation cannot be a parallel reality with conscious individuals.
If that were true.. every computer game character would be conscious and self-aware.
The idea is quite ridiculous.

Need harmonic brainwaves to soothe your diligent mind? Visit bryanel.com & relax!