Palm Pre has yet to release more information on their verison of the app store and the pricing model behind releasing Palm apps.
However, today they opened up to developers a preview of their Mojo SDK which can be accessed here. If you’ve got some time (approximately an hour) watch this O’Reilly Webcast with Mitch Allen, Palm’s Software CTO, about developing applications with their development kit. Also, they’ve got the first chapter of their webOS available for free. Enjoy.