[scraplab]

Chromium is open source and both Google and Microsoft do whatever they want to it as part of developing their browsers. WebKit on iOS is a closed source blob of rendering engine and assorted bits that it is not possible to deeply extend or alter.

[mirashii]

WebKit is also open source. https://webkit.org/

[acchow]

Yes, you can use open source WebKit to make a browser for Windows or Mac.

You cannot for iOS. On iOS, you have to use the WebKit framework. Your app will not be compiled with any WebKit open source code.

[sunnybeetroot]

None of what you said is incorrect.