Bill 6, You pick up on the equivalence principle, but you ignore one of the basics on which Einstein based both SR and GR. The measured speed of light is the same in ANY reference frame. It doesn't matter where the light is coming from or what motion the source may have with respect to the reference frame of the observer it still travels at the same speed. Since the speed is constant the only variable left is the frequency. So it is red shifted if it moving away from you, or is coming out of a gravity well.

Remember that one of the problems that Einstein addressed with SR was the failure to detect a change in the speed of light depending on the direction of motion. The Michelson-Morley experiment was expected to find the difference based on the direction of movement of the earth. It failed, and created a significant problem for Newtonian physics. SR, based on the fact that the speed of light is constant for all observers took care of the problem.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.