All sources of power require some amount of mined materials, even if its just in construction. Nuclear waste is much less problematic than CO2 emissions, and nuclear power has the advantage of providing a consistent base load.

The problem is that the GPL states:

You may not impose any further restrictions on the recipients’ exercise of the rights granted herein.

Red Hat are arguing that they are free to punish customers from exercising their rights under the GPL, and that punishment does not constitute a “restriction”, even though its done specifically to discourage people from exercising those rights. Whether Red Hat have found a loophole is something for the courts to decide, but it’s clearly against the intention and spirit of the GPL.