True, but the instruction set architecture doubles by size, resulting in larger binaries and more executable code to fetch from memory. As an example, the ARM instruction set is 32-bit by default, but ARM processors support a 16-bit Thumb mode. The programs typically execute slower in Thumb mode but often completion speed results in a net gain when the program is being loaded from slow flash/ROM. This is a typical set-up in many embedded systems.

He couldn't move to another license even if he wanted to. The contract works both ways: you are allowed to copy, modify and redistribute their project under the terms of the GPLv2, but any contributions sent to Linux must also adhere to the same terms. Thus, the contributions are GPLv2 and, without written consent from all contributors, changing the terms(license) is out of the question. He could, of course, change the license to the bits he wrote himself since he owns the copyright to them, but they only account for a small fraction of the whole kernel.

Actually, forcing everything down is not the most efficient way to save power - at least when it comes to CPU frequency governing. Dropping the speed does in indeed decrease power draw, but dropping the speed to 50% won't save 50% from the power draw, but it does double the calculation time and prevent the CPU from entering deep sleep states. It's often more power efficient to throttle up for the calculation, finish as fast as possible, and then enter sleep state.