Another excerpt from the GPLv3 that explicitly describes and disallows what Red Hat is doing - you are explicitly not allowed to add any restrictions when you redistribute GPLv3 licensed software:

If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term.

....aaand an additional excerpt which disallows Red Hat's restrictions:

Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License.

(note: "original licensors" is not Red Hat regarding any software other than their own. Red Hat cannot change or infringe upon rights received from upstream.) and ANOTHER excerpt:

If you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code.