This is huge news. ResearchKit was promised as open source and I was amongst those who were a little sarcastic on the chances of it happening. However, it's happened, and in spectacular style too. Hosted on GitHub and already accepting pull requests! Several members of the ResearchKit team are actively participating in discussions on pull requests and there's already real work being done.
It even looks like PRs for CocoaPods and Carthage support will be merged. How times have changed... Bravo Apple.
Is this a one off or is this the start of a new thing at Apple? Time will tell on that but I wouldn't get your hopes up for an open source UIKit just yet 😀.