Albert Barnes Commentary Joshua 9:24

"And they answered Joshua, and said, Because it was certainly told thy servants, how that Jehovah thy God commanded his servant Moses to give you all the land, and to destroy all the inhabitants of the land from before you; therefore we were sore afraid for our lives because of you, and have done this thing." — Joshua 9:24 (ASV)

It was mere fear that drove the Gibeonites to act as they did. They sought union with God’s people, not for its own sake, but to save their lives. Rahab’s motives were higher (Joshua 2:9 and following). Therefore, she was adopted into Israel; the Gibeonites remained forever slaves of Israel.