A correction
Based on a quick research, the the DC-3 was license built in the USSR and then modified to suit local needs (
Lisunov Li-2 - Wikipedia ). So calling it a knock off is incorrect. As to the terms of the license, or royalties, that is another matter.
The B-29 however was reverse engineered without US consent. The Soviets were preparing for the next war that was looming ( the cold war ) and needed a nuclear capable bomber which they did not poses. They confiscated all US bombers that landed in Soviet territories in WW2. Those were the source of reverse engineering and were designated Tupolev TU-4 (
Tupolev Tu-4 - Wikipedia ).
Isaac