At Apples WWDC this week, the company said that applications written as Carbon applications, such as Microsoft Office and Adobe Photoshop, would be the most difficult to port to Intel-based Macs. Apple also encouraged developers to open their source code to other developers and to use open source to help with the switch.
Apple announced on Monday that it would switch its entire line of Macs from PowerPC apps to Intel processors. At a Worldwide Developers Conference session called Mac OS X State of the Union, Bertrand Serlet, Apples senior vice president of software engineering, told the audience of developers that they should enable their Mac software to be processor-independent, running on both PowerPC- and Intel-based Macs.
News source: eWeek