Is Objective-C only used for development on Mac OS/iPhone? [closed]

Answer 1

GNUstep is actually much more active than most people think it is, and very worth keeping an eye on. It's not hard to create apps that work across GNUstep and Cocoa (meaning potentially on OSX, Win, Linux, BSD...)

These links are definitely worth checking out for anyone interested in the topic:

http://www.gnu.org/software/gnustep/information/aboutGNUstep.html

http://etoileos.com/news/

http://www.nongnu.org/gap/

Then there is Cocotron, an "open source project which aims to implement a cross-platform Objective-C API similar to that described by Apple Inc.'s Cocoa documentation":

http://www.cocotron.org/

EDIT: For an example of a commercial cross-platform product built with GNUstep, check out Eggplant.