BE400 Captain is cleared to taxi via Runway 6 at SGJ and shortly after turning on to runway observes small aircraft landing opposite direction. Aircraft lands and turns off prior to reaching the BE400.

Narrative

Was cleared by Ground Control to taxi from FBO ramp to Runway 31 via right turn from ramp; cross approach end of Runway 2; taxi via Runway 6; hold short Runway 31. Repeated instructions and began taxi. Shortly after turning onto Runway 6 (2;701 FT in length) observed single engine aircraft to be making a close in left base to final for landing near the approach end of Runway 20/24. Stopped taxi checks and focused on landing aircraft which landed on Runway 24 directly into our taxi path. Immediately brought aircraft to a stop and queried Ground regarding the approaching aircraft. Was told to hold position. The aircraft (an aerobatic tail wheel low wing with poor over the nose visibility) was now rolling out drawing closer to our position at which time I once again questioned Ground Control regarding the decreasing distance and was told to hold position. At this point we did not move the aircraft forward; but I as Captain stated that I had the aircraft to the Second In Command who was the pilot flying and prepared to exit the runway into the grass. Just prior to reaching our position the oncoming plane exited the runway via Taxiway D3. We were then cleared to continue taxiing via Runway 6 to 31. This is the closest incursion I have observed in my career and it scared the heck out of me! Contributing Factors: Choice of Controller to issue taxi via active runway as opposed to taxiway. Landing aircraft on Tower frequency; taxi aircraft on ground frequency; both on active runway. If it necessary to taxi onto the runway in use allow Tower to control all aircraft utilizing that runway whether taxi or takeoff/landing.