The thread title says it all. To clarify, though, I am specifically referring to the version that Naruto used against Kakuzu, not the one that can be thrown (I don't think Kakashi has seen that version anyway). Here is why I think that Kakashi copied the Rasenshuriken.
1. We know that Kakashi knows the Rasengan, since he used it while Naruto was developing his original Rasenshuriken. He was even better at using the technique than Naruto is.
2. Kakashi previously was working on infusing nature-based chakra into the the Rasengan, but when he failed, he decided to create the Chidori.
3. Kakashi has used every nature type except for wind, but I assume that he can use it as well, but either hasn't seen very many wind-based techniques or just prefers not to employ them. To further support this, many of the wind techniques in the series require some sort of weapon (ie. a fan or chakra knives).
4. Kakashi had his Sharingan activated when Naruto first used the Rasenshuriken against Kakuzu.
1. We know that Kakashi knows the Rasengan, since he used it while Naruto was developing his original Rasenshuriken. He was even better at using the technique than Naruto is.
2. Kakashi previously was working on infusing nature-based chakra into the the Rasengan, but when he failed, he decided to create the Chidori.
3. Kakashi has used every nature type except for wind, but I assume that he can use it as well, but either hasn't seen very many wind-based techniques or just prefers not to employ them. To further support this, many of the wind techniques in the series require some sort of weapon (ie. a fan or chakra knives).
4. Kakashi had his Sharingan activated when Naruto first used the Rasenshuriken against Kakuzu.