The Iconfactory is one of the premiere Mac development houses, and as Iconfactory developer Craig Hockenberry posts on his blog, they've just contributed to the developer community "in a big way."
The team has introduced an open source framework called Chameleon, which provides apps designed for iOS an easier porting path to run on Mac OS X as well. Most of the work came from tools built to handle Iconfactory's own apps, but they've released the code to other developers interested in reusing iOS code for Mac OS apps.
A lot of the ins and outs we'll leave for the developers to figure out (the project page admits that Apple may