For a Sharigan or any eye to be use by a non member of a clan it must be taken and inserted in it's new host active,Both Kakashi and that Guy with the Hyuga eye are prime examples, that is why they both have them covered when not in use or they would die from chakra depletion. The victim must be alive and probably drug, Obito gave His willingly to friend, but enemies must use some kind of drug to keep the eye active for transplant,otherwise the victim would turn it off and the enemies can't use it.