[pvonk]

Like Bento, many developers are being forced to discontinue integration with Calendar and Contacts due to Apple's deprecating the links to these databases in their development tools. My understanding, after communicating with BusyCal, is that they have developed their own code to maintain connections to Calendar (since it is the main reason for their software). Others, like Bento and (I believe) Omni, do not have this as their primary focus, hence they are dropping integration.