Is the contract restricted to the buyers, or to the "any 3rd party" of the GPL?

This is a separate issue. The reason we have consumer law is that the common law didn't cover these scenarios. So if you bought something from a retailer, you only had rights in contract with the retailer, and generally most of the rights you might expect to have could be contracted out of. If you wanted to make a claim against the manufacturer it would need to be something like a claim in negligence, which was much harder to establish.

In New Zealand, consumer warranties can always be pursued against both retailer and manufacturer, except for a few specific warranties which are only available against the retailer. And it covers gifts as well. They're not contractual rights but statutory rights and it's covered specifically in the Act. But this is just a matter of statute - it has really nothing to do with contract law.