Hey Jure, just a tiny comment regarding slide no. 5... :)
If it's that simple, then why doesn't Apple just opensource the whole browser? Yes, it's not that simple. Actually, it would be better to say something like "Safari = KHTML + Cocoa + Secret Internal APIs".
Apple is using lots of secret internal APIs, which provide a way for them to communicate to different revisions of Mac OS X. This approach isn't opensource friendly, nor is it that different from what was Microsoft doing in the late 90's.