As a software developer and farmer (and owner of some John Deere equipment), it doesn't seem that unbelievable to me. I know quite a few farmers who also work in tech. The capital intensive nature of the business means that many come from other high paying professions, of which tech jobs tend to be among, to support the habit.

Although from everything I have read on the subject, source code does not really seem to be what people are after. They just want to have equal access to manuals and tools that the authorized dealers have. The guy in the service truck isn't modifying source code either.