GM trying to keep you from modding your vehicle

Its always risky to read parts of an agreement. The linked article only cited a sentence apiece from John Deere and GM. Without seeing the entire agreement/purchase document, it appears that they are saying that the purchaser only has a license to use the software embedded in the various control systems and not the right to modify (and or sell either altered or unaltered) the software.

I believe that's a reasonable position to take, but I also believe the suggestion of establishing licensed repair stations is a reasonable thing to do as well.