Palm continues to provide a very old version of Palm Desktop 4.2.1D for Mac users, enabling legacy Palm Centro, Treo, Zire, Tungsten, LifeDrive, and Pilot models to synchronize with its Mac OS X Universal Binary desktop software. That software is based upon what was originally Apple's Claris Organizer, which Steve Jobs sold to Palm over a decade ago as Apple divested itself of its already long in the tooth Claris apps.
In concert with launching its Macs as the "digital hub" and selling the iPod, Apple developed iSync for Mac OS X, which enabled devices from any manufacturer to sync their data with a common store shared by desktop apps including iCal and Address Book. It eventually allowed users to also sync that information with Apple's .Mac service, now called MobileMe.
Palm never bothered to update its Palm Desktop for Mac software to make it compatible with Apple's iSync, but Apple, in an effort to keep Macs compatible with Palm's device, created its own Palm Conduit software that linked Palm Desktop's HotSync system into iSync. This software was then incorporated as part of iSync 2.0, released as part of Mac OS X Tiger nearly half a decade ago.
With Palm all but abandoning its "classic" devices developed prior to the new Palm Pre, which does not use the same legacy Palm OS nor its HotSync or Palm Desktop software, the value of maintaining HotSync support in Mac OS X has dropped dramatically, leaving Apple to cut the support from the version that ships with Mac OS X Snow Leopard entirely.
It does not appear that the discontinuation of legacy Palm OS support in iSync is at all related to efforts by Palm to trick iTunes into syncing data with the new Palm Pre as if it were an iPod. While Apple doesn't provide a public syncing system for using iTunes, it does provide public APIs for any developer to hook into Mac OS X's Sync Services.
Third party software, including the Missing Sync from Mark/Space, enables Mac users to sync calendars, contacts, bookmarks, music, documents and other information between older Palm OS devices as well as other hardware including the new Palm Pre, BlackBerry, Symbian, and Windows Mobile phones and the Sony PlayStation Portable.