Sources: Opera , , 
quote: Consider that WebKit is itself a fork of KHTML... Consider also how different Safari and Chrome are, despite sharing the same layout engine. There's a heck of a lot more to a web browser than the layout engine.
quote: Browser diversity ... common render engine ... seems to me to be a perfect sort of set up
quote: Multiple independent developers with their own engine help encourage innovation and enforce compliance between all parties.
quote: I disagree. Multiple independent developers with their own engine help encourage innovation and enforce compliance between all parties.
quote: Some interesting results are the share of contributions by the two main companies behind the project (Apple and Google), and how it has evolved from a project clearly driven by Apple, before 2009, to the current situation, with Google leading the top contributors table, and both Apple and Google being almost equal in contribution share over the whole history of the project. During the last years, it is also noteworthy how the diversity of the project is increasing, with new players starting to show a significant activity.