I can't say much as far as how the GM files were obtained, but as far as the DSM stuff I'm into, a group of like minded folks put in a lot of work and research to disassemble the code. From reading through some old archives from Todd Day(pretty much the pioneer for DSM code hacking), I do know that he had some help from the GM community.
All of the DSM ECU code related documents and files are on the Yahoo group, and there is a Jeep group, as well as a Dodge group. Give it a shot if you haven't already. http://autos.groups.yahoo.com/group/jeep/
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