David lived with Achish at Gath, he and his men, every man with his household, even David with his two wives, Ahinoam the Jezreelitess, and Abigail the Carmelitess, Nabal's wife.
Why would David have been welcome in Philistia? Probably Achish and the other Philistine lords rejoiced to see the rift that existed between David and Saul.