Pilot taking off from a non-towered airport reported they observed another aircraft taxiing across the runway just as they were rotating. Pilot reported they flew over the aircraft.

Narrative

During engine start on the ramp; we heard a radio call from an aircraft planning on landing runway 17 within the next ten minutes. We started our engines and completed our checklists and taxied to the end of runway 31. I announced 'Aberdeen traffic Aircraft X taxiing from the ramp to runway 31.' over the unicom frequency. At the end of runway 31; we checked the traffic on final approach and also any traffic on the runway visually; we determined it to be clear. I made another call on unicom: 'Aberdeen traffic Aircraft X departing runway 31 straight out departure Aberdeen traffic' We completed our runway lineup checklist as we taxied onto runway 31 and began our takeoff roll. I called V1 and then rotate at the appropriate speeds; just as we were rotating; we noticed Aircraft Y taxiing across runway 31 on taxiway Alpha in front of us. We were getting airborne at the time and no evasive action was needed. We passed over the other aircraft at about 50 feet AGL. We were on an IFR Flight Plan and were released at that time. In the future; when departing from uncontrolled fields; we plan on being more vigilant as to communicating with other airplanes to help keep mistakes from being made.