This doesn't sound right at all. I'm gonna need some more proof. I remember reading Shiggy coded DK himself when he was tasked with converting N's Sea Hunt, or whatever machines into something else. He actually wanted to make DK a Popeye game, Bluto would have been DK, Olive would be Pauline and Mario would have been Popeye. Nintendo couldn't get the rights at the time or something like that.
You mean Radar Scope.
And Shigeru Miyamoto isn't a programmer.
You're not going to get the "proof" you seek, because Nintendo settled with Ikegami Tsushinki out of court due to a lawsuit regarding the rights to the game's code in the early 80's and they will likely never make this information available to the public. But it is absolutely true that elements of Nintendo's early arcade works were outsourced for programming purposes.
Read this article if you'd like to learn more.
And Nintendo doesn't own the rights to this code either?
I'd have to assume they do, but have no interest in re-releasing it on its own, for whatever reason. They have re-released Donkey Kong 64 on the Wii U Virtual Console, which contains this version of the game.
There is definitely a complex relationship between Nintendo and the rights to the arcade versions of Donkey Kong and Donkey Kong Jr. We simply don't know all that much about the situation, because Nintendo hasn't made this information public.