Totally misleading title. "Polls" is one thing, poll aggregators are a whole other thing. I was really excited to read about actual polls that are somehow open source (not sure how that would work though).
Open source would not be nearly as impressive as reproducible.
Yes, although is reproducibility even possible in polls? People's opinions change on a whim. In fact people's opinions can change simply because they were asked a question so the answer might be different if asked the question again,
I guess you could conduct the same poll with multiple sets of people and see how the results compare, but in a way that's what poll aggregators do.