It’s Chromium’s non-Google cousin.
If that piques your interest, be aware that it’s mostly Apple’s baby.
And to swing back positive again, it’s open-source because Apple didn’t create it in the first place and they’re bound by GPL to keep it that way.
Finally, a useful fun fact: WebKit GTK often comes with a MiniBrowser
program that is a bare-bones web browser wrapped around the engine.
It isn’t symlinked in /usr/bin
or anywhere like that, but it does work as an emergency secondary browser if something breaks your main one.
It’s usually found somewhere like /usr/lib/{OS type}/webkitgtk-{version}/MiniBrowser
On my machine it’s /usr/lib/x86_64-linux-gnu/webkit2gtk-4.1/MiniBrowser