This is good news for Apple, as WebKit will gain some ground in that area, but not very surprising when you think about it. To use the host OS native web browser engine is not an option since it unecessarily would make Apollo less platform independent; the Internet Explorer engine is also out of the question since it isn’t supported on any other platforms. Then there are Gecko, Opera or developing a new one. The latter is too much work, and not worth it. Opera would probably work, but they are quite marginalized as it is and Opera is currently focused on the mobile market. Then there is Gecko, but there is a reason why Apple chose to go with KHTML and not Gecko a couple of years back: Gecko is huge, a beast. WebKit, née KHTML, is leaner and has already shown that it can be ported to mobile devices. The FAQ actually states that WebKit was chosen because it had a “Minimum effect on Apollo runtime size” and “Proven ability to run on mobile devices”, which Gecko doesn’t.
Oddly enough, this isn’t in line with Adobe’s recent decision to give away the ActionScript runtime to the Mozilla foundation. But on the other hand, that doesn’t really have anything to do with Apollo.
I’m really looking forward to see what Apollo will be able to do. In my mind it spans the web-desktop divide which is quite exciting.