Pilot crossing a runway at a non-towered airport reported a near collision with another aircraft taking off on the same runway.

Narrative

After landing on Runway X; made radio call on UNICOM that we had cleared the runway. We were taxiing with bright landing lights and taxi lights; very brightly illuminated; and heard a low volume radio call on UNICOM we believed said the aircraft was 15 miles north and inbound. While taxiing we announced we would be crossing Runway XX-XY on the ground; heard no response; paused to make sure no one was using the runway; when a Piper went by in front of us; apparently taking off on Runway XX. We braked; separation was ~250 ft.; the Piper took off successfully. We received no conflict warning on our ADS-B Traffic screen; which was displayed on a MFD (Multifunction Flight Display).While a non-event; a few seconds difference in timing could have resulted in a collision. In retrospect there was a conversation going on in our aircraft that may have interfered with our understanding of the radio call; and the call was very low volume and brief. We also expected activity would be on the runway we had just used (X); and were not expecting a departure on XX. Finally; we are now modifying our behavior to keep a sterile cockpit when a taxi route might possible involve a runway crossing.