Reasoning behind the "preferred form" language in the GPL

To be honest, I'm a bit on the fence myself here, but I think we're looking at it from the wrong angle, or at least we should consider what RH is doing with their terms. The areas of their terms of use you're mentioning here is basically "don't ape our service" language. Without it, someone could literally buy a single RHEL subscription, get the system updates, and mirror said updates for a charge to others w/o RH having any recourse against said organization.

Put another way, RH is saying that in order to continue to use their service (RHN updates + support), you can't compete with them by using their own work product. Technically, you're free to do with the code as you wish, but certain actions may result in you not having access to RH provided services in the future.

Does the GPL state that no matter what someone does with GPL based code, once a vendor ships it to an entity, the vendor is forced to continue a business relationship with the entity? Keep in mind the source for the GPL'd code is still available as SRPMS IIRC, so RH is still distributing source for anyone, including said entity, to download and compile for themselves. The entity just looses access to the value added services RH provides.

As I said, I'm a bit on the fence myself, but this is another perspective to consider,