Did he give it [for a gift]?
Radak: He wanted to give, but David did not want to receive a gift.
Why is he called "Aravnah ha'Melech"?
Rashi: He was the [chief] officer of the Yevusi.
Radak: He was king of the Yevusi dwelling in Yerushalayim. Even in the days of David the Yevusi were in Yerushalayim, just like they remained after Yehudah conquered [Yerushalayim] - "va'Yeshev ha'Yevusi Es Bnei Yehudah bi'Yrushalayim Ad ha'Yom ha'Zeh" (Yehoshua 15:63). They paid taxes; they had houses, fields and vineyards via the tax, that they served Bnei Yehudah and Bnei Binyamin. Even after David conquered the Metzudah, he let them live in the city to pay taxes. They were there until Shlomo built the Beis ha'Mikdash.
Radak: Some texts of Targum Yonasan say 'Aravnah gave to the king what the king asked from him.'
Yevusi is one of the seven Kena'ani nations. We are commanded to kill them!
Radak: This Yevusi was not from the seven nations, rather, from Pelishtim, from the seed of Avimelech. It was permitted to leave them in Eretz Yisrael, since they accepted not to serve idolatry and the other Mitzvos of Bnei Noach. Even the seven nations may dwell in the land if they will [accept their Mitzvos, and] not cause us to sin - "Lo Yeshvu b'Artzecha Pen Yachati'u Oscha Li" (Shemos 23:33).
