From The Memoirs of John Parker Hammond...
"Dennis Nedry I found in Cambridge, and despite his idiosyncrasies, he was years ahead of his competition. Dennis fancied himself quite the hacker; he had his own locks for his doors. His office decorations were quite outside company regulations."
"It was 3 A.M. The room was strewn with soda cans, and for the hundredth time we ran the extraction sequence. As Nedry typed, the world seemed to hold its breath, and for a moment we stood at the turning point between two great planetary eras: the million-year reign of man, and the age of the dinosaurs. "Dennis? What are we looking at here?" All my life I waited for something great, something extraordinary. And then... it opened up. The code read true."
"In 1989, the park was nearly complete. Our investors demanded on-site approval and I, idiotically as it now turned out, believed we were ready. The debacle of August 27, 1989 is now quite well known, and the legal consequences were, as you may well imagine, rather extensive. I still believe Nedry left himself a back door, something about the hobbits or god knows what."
From Jurassic Park - "I am totally unappreciated in my time."
Nedry obviously turned to a rival company because he felt as if he was the real miracle worker. However he saw money as a show of appreciation.