failed to mention that I doubt YAP6 is necessary. If it can produce a mostly working perl 6 implementation in a short time frame that is at least as fast as perl 5 - great. I suspect that this is not the case. I guess what I am saying is not all non-core projects are bad - but, for me, the jury is out on YAP6.
You know, that is exactly the point. Before I started thinking about YAP6, I was working to bootstrap KP6, as to release it from MP6 and make it self-hosting. But when I finally got a bootstrapped compiler, it was taking like 20 seconds to compile a simple "say 'Hello World'" line. That was when I realised that the problem was on the fact that KP6 was implementing a runtime enviroment on top of perl 5, which is by itself already a very heavy runtime, and when you stack them, the performance is absolutely unpractical.
At that point I started to take a deeper look at Parrot, that was also during YAPC::EU::2007, while I had a very good chatting with the parrot folks, and that was when I realised that Parrot has taken a very hard challenge, and that IMVHO, if I wanted something to happen faster, I would have to take a simpler challenge. And that's why YAP6 started in the first place. YAP6 is nothing but a port of the KP6 "object system" to C, as so instead of generating weird perl 5 code, KP6 could generate weird C code that would run faster. Of course generating PIR was a possibility, but (and this is completely my fault), I just couldn't get out with PIR and parrot internals requires skills that I don't have.
As the ROADMAP and the README says, YAP6 intends simply to be a runtime library for KP6 to be built upon. It is simply the KP6 object system translated to C.