Runers on 2nd and 3rd. B1 hits and defense makes play to home. first runner safe because cather drops ball. Second runner heads for home as cather goes for ball and gets tied up from the first runner and can't get to ball so the second runner scores, is he safe? any interference?

need more info, sounds like a had to be there type play

Thats just a judgement call. With the first runner coming home, there is going to be contact. You just have to judge weather the runner intentionally interfeared. If you are unsure about what to call, go with the no call.

Interference does not have to be intentional, but with a runner sliding into home I can easily seem him being in the way of the catcher trying to pick up a dropped ball, and not have any choice, ie can't move any faster than he is moving to get out of the way. This would be pure judgement on the umpire but from the description I would not likely call interference unless it appeared to be intentional. I assume if it appeared intentional you would not be asking this question.

Like you said, interference doesn't require intent, but in a case like this it would require at the very least negligence. You have to give the runner the benefit of normal human reaction time - he can't simply vanish. If he's TRYING to get out of the way, and just does a poor job of it, I have no call.

If he just sat there, (on top of the ball, for example) and made no effort to move, I might call interference.