If you allocated power to Caereus Residential, and read the laptop entries, you would know that Dude, aka John Dyson, was actually an important Biocorp scientist working in the Deep Caverns. After returning to the surface, the first thing I did was visit Rail Crossing and speak to Dude, but there was no additional dialogue options. I really don't get it. You find this wacky guy called Dude in Rail Crossing, you then learn he's actually a genius in the field of Psionics and was working in the DC during Biocorp's final days, he's also managed to halt his aging process, and you can't say a thing? I think you should at least be able to ask:
How did he escape the fallout of Biocorp's collapse?
How has he lived so long? (Already implied, but could use more detail)
Are any other Biocorp engineers alive?
What we he researching? (Again, implied, but could be given some more detail)
What can he say about the Monoliths?
Can he teach you anything?