If you already have a published app, then you can apply to be part of the program but the announcement says:
"But I do want to set your expectations that program access will be limited."
The public SDK will be made available "later this year" which is behind the time table that developers were led to expect.
As you can imagine, the developer community, judging by the comment stream, is less than happy.
What makes this whole strange development even more strange, is that the announcement was made on the day Nokia previewed a range of WP8 devices.
The Nokia launch got most of the publicity, so perhaps the idea was that a little negative news wouldn't be noticed.
The real question is, why the limited availability?
Is there some dark secret lurking in the SDK?