Anybody can shoot a movie too. Just because it didn't come from the golden brain of George Lucas doesn't make it less valid. Nor did Lucas ever directly address the issue in the films, so using the films to defend why it should be allowed is rather moot, in my opinion. Pointing to the "luck" of R2D2, that does not imply that R2 was using the force. Simply because one cannot feel it surrounding them does not mean it doesn't guide them. Han Solo is a perfect example of this, and he has plenty of quotes to his name for "verification."
If midichlorians were to be harvested, the question then would be: is the imitation of life also life? Mass Effect spent three extraordinarily long games trying to answer this question and I don't think they reached a proper consensus either (c wut i did thur?). I personally have a difficult time recognizing droids as being "intelligent" because, in the end, they run based on a program. Programs are not adaptable to changing environments. Adaptability is fundamental to life. Droids that show "intelligence," perhaps like C3P0 or R2D2, are extremely rare and quite random cases. Programming a droid with this kind of adaptability (in the universe created by Lucas) is something I can't reconcile.
Can droids use Force abilities? No, see above reasoning why they can use the Force. But can they use imitations of Force abilities? Possible. I imagine that Force push is rather akin to many sonic-type weaponry. Force pull could be interpreted as some kind of tractor beam. Force Lightning, well anything electronic naturally generates electricity. Discovering how to properly harness it would be difficult but probably not impossible.
I think there are plenty of other clever solutions to uncovering the problems put forth here than trying to logically sift through the moral implications of whether or not droids are alive.