Reading up on the subject elsewhere, I discovered that the tether would be powered by the ISS solar wings, and would generate a small force sufficient to raise the ISS to a higher orbit. Alternatively its motion through the ionosphere while unpowered would generate electricity and dissipating this power with an electron gun would cause the spacecraft to sink and eventually de-orbit.

So real propulsion requires a solar/nuclear power source for the tether and an ionosphere to repel. This might actually qualify as a "reactionless drive", although not technically accurate, would not need chemical propellant.

Tethers have been proposed as slingshots to raise/lower spacecraft too. Dr. Forward's major suggestion was the "Rotavator", or Rotating Space Elevator, which was a rotating tether in low-earth orbit that would grab payloads from a high-altitude aircraft and lift them into space. The problem is that the Rotavator would require stationkeeping propellant.

Hmmm..... Why not combine the two --- A Rotavator with ProSEDS for stationkeeping.