Just because it's opensource doesn't mean there are anyone with the skills, knowledge of the codebase, and the time and inclination to do a port. The trouble is, it's a big complicated project based on X11 and worse, GTK+ (a Linux graphics toolkit originally made for the Gimp, but since used for the Gnome desktop and other associated apps). This version uses the Quartz-version of GTK, which makes it a bit more native and easier to port, but it is still slow and clunky and despite a skin doesn't quite fit in, for instance the Open/Save dialog and the way the pallets and windows behave and widgets look, feel and act. To make a completely native version is a major undertaking requiring basically a total rewrite using Xcode and native frameworks where available for some functions instead of the myriad of Unix tools duplicating the native APIs, but most importantly in the GUI parts.
How times have changed.
). But always wanted to give an answer for people asking about a graphics editor no so full fledged and expensive as PS.
