Gornaut states that momentum is being transferred from the supersonic incoming air flow to the engine
That would be drag as something has to slow the air down. This thread caused endless discussions a while back. The way it was originally phrased you would think you had the basis for a perpetual motion machine, ie just bend metal into a sophisticated shape and off it would fly ! Need to take a holistic view of the whole power plant to really get the picture, hence the quotes above. My view was that it was really about the efficient recovery of pressure for the intake but what do I know: certainly the intake on its own isn't a prime mover or the active source of any thrust.