“never cease to be.” The Hebrew “cease” is the same word as “cut” in “cut a covenant.” The people of Gibeon cut a covenant with Israel and now some of them will never be “cut off” from being a slave and serving in the Tabernacle or Temple. However, some would consider it a blessing to be a non-Jew and get to serve like that in the presence of God.
“to the house of my God.” The Gibeonites became slaves to Yahweh and also served Israel (Josh. 9:27). They were alive because of the commands of Yahweh.