Albert Barnes Commentary 1 Kings 9:22

"But of the children of Israel did Solomon make no bondservants; but they were the men of war, and his servants, and his princes, and his captains, and rulers of his chariots and of his horsemen." — 1 Kings 9:22 (ASV)

Comparing this with 1 Kings 5:13–14, it would seem that a modified service of forced labor for one-third of each year was not regarded as reducing those who were subject to it to the condition of bondservants.