First point. Itachi was arrogant about "Being a true Sharingan Master" and saw Kakashi as a lowly wannabe, even with his similiar blood. So he was arrogant to use his ultimate ability.

So we know Kakashi has similar blood.
We only know that if you have Uchiha blood you can perform it. It doesn't rule out having "suitable blood".

It also says nothing about copying it.
There is a difference between - Performing and Copying (learning).



btw on a sidenote: DID anyone think Sasuke copied it, seeing how Itachi used it on him? haha - I completely overlooked this