Pre-orders and previews begin April 10, launches April 24.
Apple to Allow Free iPhone/Touch Apps Without Special Approval?
Electronista, however, now claims that Apple plans on only imposing those restrictions on commercial applications for sale through iTunes and will not try to restrict free programs in any way
...the new contact claims that free applications are not subject to the same rules that will guide paid software downloads. In this model, free software is unlikely to be subject to much if any scrutiny by AppleSuch a tiered system could appease those concerned that an Apple approval system would arbitrarily restrict an otherwise thriving developer community. Meanwhile, commercial iPhone applications sold through the iTunes store would benefit from the existing infrastructure and customer base of the iTunes store, but in exchange would have to meet some set of predefined criteria.
It is still too early to draw too many conclusions about Apple's SDK plans. Apple has announced very little publicly about their plans, though Apple's COO has recently made comments claiming that with the SDK, the only limit would be people's imaginations.
Apple is hosting a media event on Thursday, March 6th to detail their SDK roadmap.