I'm glad that they ended up releasing it, but to show that as an example of open source from Apple ... indeed shows that people have short memories ;-)
You say "they couldn't collaborate" I say "Google really wanted to compete".
Remember that it was Google who decided to perform a fork because they had a different approach than Apple for how "multi-process" should be implemented. Google had an implementation that they didn't want to integrate into the Webkit branch - hence the Blink fork.[1]
Also Apple would have been happy if they could use the Google's implementation instead of using their own - they said that repeatedly [2]
You can also find more details of the story here. It looks more and more obvious that the decision to create a WebKit fork was more political than technical : https://news.ycombinator.com/item?id=5490242
[1] https://www.theguardian.com/technology/2013/apr/05/blink-goo...
All I'm saying is that Apple's WebKit is not a good example of OSS and if that's what you have to show for iOS, then it's a really sad state of affairs.
People really have short memory and unfortunately have too much biais to even make a simple Google Search to get some informations. Trying to define this as "one is better than the others related to X" is childish at best.
https://developer.apple.com/opensource/
Warm vibes,