Vista Kernel API?

There has been or I have been having confusion on the Vista kernel situation. I've heard from many sources that the kernel will be locked down from any third party, that's why Symantec and Mcafee have gone crazy. But, Steve Gibson mentioned that Microsoft will only open up the kernel to other parties through an API and that API will only be used on the x64 Windows Vista. I would really like to know what Microsoft is going to do. I don't see why Microsoft would release an API. Microsoft is doing a very smart thing by locking the kernel down.
By the release of the API to security companies they are opening the kernel up to the hackers and other nasty rootkits and malware. It would be very smart to lock the security companies out of the kernel and to only keep the kernel open to themselves. It's a win-win situation on Microsoft's part, they are able to keep the hackers, and rootkits out and also beat other security competitors by Windows Live OneCare only having access to the kernel. It will be very interesting to see what Microsoft does here.