Let me just say it: We want native third party applications on the iPhone, and we plan to have an SDK in developers’ hands in February. We are excited about creating a vibrant third party developer community around the iPhone and enabling hundreds of new applications for our users. With our revolutionary multi-touch interface, powerful hardware and advanced software architecture, we believe we have created the best mobile platform ever for developers. . . [signed] Steve

Word on the street is that it will require some sort of certification, ala RIM, but there may be a workaround allowing you to install non-certified apps, or no certification process at all.