Not technically Safari but https://webkitgtk.org is a thing and WebKit itself is open source: https://github.com/WebKit/webkit
“”” WebKit is a cross-platform web browser engine. On iOS and macOS, it powers Safari, Mail, iBooks, and many other applications. “””
Midori is also based on WebKit: http://midori-browser.org
AFAIK Safari does not provide more privacy protections than WebKit.
Some of Safari’s privacy protection (Intelligent Tracking Prevention: https://webkit.org/blog/7675/intelligent-tracking-prevention...) uses APIs in iOS and macOS that aren’t part of WebKit.
Safari is pretty good at privacy protection. Apple doesn't really have an interest in collecting your data and they have a history of implementing features improving privacy (cross-site tracking protection, build-in adblock API, etc.).
The problem is that Safari is only available to the wealthiest in the world.