Would it be against the law for you to build one for your use or your friend's use, if you figured out how? I don't think so.

Now, it depends on the product, but in the case of the "Ginger", it would be illegal to manufacture and distribute a copy of the product. It's called a PATENT, and I'm sure the Ginger is so loaded with patents that you can't even talk about copying it without a team of lawyers descending upon you.

The thing is that Patents are different than copyrights. And copyrights are different than trademarks. It's probably a good idea for you to research the difference between these three things before discussing them.