The AK-47 is not a copy of the StG-44, but a development of an earlier Kalashnikov SMG design and is inspired by many earlier designs. (Most things are.)
The AK-47 is best described as a hybrid of previous rifle technology innovations: the trigger, double locking lugs and unlocking raceway of the M1 Garand/M1 carbine, the safety mechanism of the John Browning designed Remington Model 8 rifle, and the gas system and layout of the Sturmgewehr 44. Kalashnikov's team had access to all of these weapons and had no need to "reinvent the wheel", though he denied that his design was based on the German Sturmgewehr 44 assault rifle. Kalashnikov himself observed: "A lot of [Soviet Army soldiers] ask me how one can become a constructor, and how new weaponry is designed. These are very difficult questions. Each designer seems to have his own paths, his own successes and failures. But one thing is clear: before attempting to create something new, it is vital to have a good appreciation of everything that already exists in this field. I myself have had many experiences confirming this to be so."
The PRG-7 is a development of the RPG-2 which is basically a slightly improved Panzerfaust 250, a prototype German weapon.
The MiG-15 and F-86 are both products of German science and thus it is not surprising that they look similar. The only thing that was a pure copy on the MiG was its "British" engine.
The Tu-4 is an almost blueprint copy of the B-29. The Soviets were pretty desperate for a long-range bomber after WWII and the advent of atomic weapons. Luckily for them a number of B-29s made emergency landings in Russia in the final months of the war. The Tu-4 was also the basis for the design of the Tu-95, so you could say that this...
... is in part a Boeing product.
