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They may have released the compiler front end, they never released their Objective-C runtime library making the code worthless and hard to maintain - apple would publish their updates as required without any of the effort necessary to stay compatible with anything but their own non-GPL runtime.

Fortunately, they don't have a monopoly on Obj-C runtimes.
http://www.gnustep.org/
http://www.cocotron.org/

I don't think the license for GNUstep would allow them to use it for that (though it is designed to allow *step apps to run on the platforms it's ported to, and there is a port to Windows which NovaMind uses).

There is Cocotron though: http://www.cocotron.org/ --- it's an M.I.T. license, so should be good to go.

I could not agree more! I've been waiting for gnustep to become usable since the late 1990's and it still is a piece of junk as of a few months ago. It would appear that the guy at cocotron http://www.cocotron.org/ has done more in a year or so than the gnustep folks have done in 15 years. I don't get it, the NeXT/Cocoa API is so logically laid out, it should be pretty easy to wrap them around GTK+ and Win32/64, but the gnustep folks are intent are re-inventing the wheel and rolling their own low level widget set. Their approach makes gnustep look just plain bizarre in Gnome and Windows. SWT has the right approach. The impression I get from on and off following the gnustep boards is they are intent on duplicating the original OpenStep API, and not faithfully following the new API which is Cocoa. It really would be awesome to be able to write a cross platform ObjectiveC app (I love ObjectiveC, have since I've learned it on a NeXTStation), but I don't know if the gnustep folks will ever pull their heads out of their own asses.

I don't know if anyone is working on it directly, but indirectly they are. UMEKit is a Cocoa port of UIKit. Cocotron is a Linux (and Windows) port of Cocoa. Combined, you have the basis of your iPhone simulator and the basic tools necessary to conduct the development process.

There's also gnustep. I won't comment on the gui side of things, but their foundation kit is solid. I'm not sure if they support blocks yet. Another option (particularly for windows) is cocotron, although that is designed for cross-compiling from x-code on a mac.

What language would you suggest? Keep in mind that Objective-C is C. If you can compile C on your target device, you can compile Objective-C to the same device. The only other option on the iPhone for native development is C++.

Objective-C has a long history of portability. OpenStep, an open standard for GUI applications, implementations were implemented atop Objective-C. You'll find numerous open source implementations of the Foundation and AppKit libraries that you may use on non-Apple devices. Granted, the open source UIKit implementations are immature at best. Even Java was heavily inspired by Objective-C.

Yes, using Objective-C and UIKit might make porting your code to another platform difficult. Of course there is nothing stopping you from implementing UIKit yourself. But otherwise, Objective-C is a fantastic choice if portability is a concern.

Cocoa is also available virtually everywhere, including the web browser itself. While not all implementations of Cocoa are open source, it is based on an open standard (OpenStep) meaning that anyone can write their own implementation.

I do agree with your underlying sentiment. The web browser should provide a virtual machine enabling developers to write their software in any language and framework they see fit. An HTML renderer could be just one of the many applications available to the browser.

While I'm not sure developing mac applications on windows makes much sense

Cocotron allows you to target Windows (and other platforms) with your Cocoa application, like OpenStep and YellowBox have done in the past. Cocoa seems to finally be realizing the dream of OpenStep and is becoming the de-facto standard for interface development on all platforms (web, mobile, desktop, etc.) It is the natural direction for Windows developers to head*. Having an application that runs on the Mac with just a recompile makes it that much more appealing.

* I have a hard time believing Microsoft would get behind the movement though.

If you can get Apps that run on iPhone and Android then inter-platform price competition becomes an issue.

Keep in mind that Cocoa Touch is based on a long history of multi-platform development. While Apple no longer maintains cross-platform compatibility with Cocoa, projects like Cocotron have picked up the slack. There is no reason why someone cannot implement Cocoa Touch for Android.

And that is exactly what Apple wants. They are pushing for a standard, like they are pushing for HTML5 to be the standard for web development.

We despised Microsoft because they used their success to push sub-standard products on those who did not want to use them. So far, I have not received an important email attachment that requires an iPad to view it.

Apple, on the other hand, is quite adamant about making content available to everyone. If you don't like the iPad, your Linux system running on the SPARC architecture can do all of the same things.

In fact, Cocoa has a long history of openness. OPENSTEP/GNUStep was designed to be a multi-platform application framework, including support for Windows. Apple, after acquiring NeXT continued development on the framework under the name YellowBox which continued to support Windows. YellowBox eventually became Cocoa with the release of OS X. Cocoa did phase out support for other platforms at this time, but projects like Cocotron have picked up the slack.

iPhone OS carries on with the tradition. The bulk of the work to bring iPhone and iPad apps to other platforms is already done. If you want to build your iPhone app for MIPS/BSD, you are almost just a recompile away. Now let's see how long it takes you to build your Flash app for that platform.

The new SDK rules are harsh, no question. But Apple is pushing a platform designed to be open right from the start. From a developer's perspective it is frustrating to know that I cannot use tools that are better than Apple's own for development. From a user's perspective, however, I am quite excited at the possibilities of Cocoa Touch everywhere. I will be able to buy a device from Acme Inc. and developers will be just a recompile away from bringing their applications to my platform, without having to wait on Adobe to choose to include support.

We get excited about the idea of one platform for web development (HTML5). Why are we so fearful of one platform for native application development?

You can see Ars Technica's writeup on the Cocoa port of QT4 for more information on how they've actually done so far.

The Cocoa API is also being unofficially open-source ported to other platforms (most actively Windows platforms) through the intriguing Cocotron project. It's still a work-in-progress, mind you.

Every portable API uses Carbon, not because of high-level vs. low-level, but because Carbon can be easily integrated with existing C/C++ code, whereas Cocoa requires a little more effort. Carbon provides what a lot of Mac users consider a sub-standard experience, and worse integration, but for most people porting their apps to Mac, they rarely know or care.

In OS X, there's not a lot of 'communication' that needs to be done to make the window 'less blank', though I'm not sure exactly what that means. You can put together a UI in Interface Builder, put your code into XCode and add whatever the Mac port needs, compile it together, and off you go.

You can write most of your app in C++, write the GUI-management code in Obj-C (or Obj-C++), and then glue it all together with Obj-C++.

Dunno about the ponies, but OpenStep (sort of) runs on Windows and gives you all the ObjC goodness you're being deprived of, and there's also The cocotron. All this can be found at the wikipedia entry which also does a half-decent job of explaining what it is that makes Cocoa so nice to use.

What the Wikipedia article misses is the simplicity of the language - it's just about right, not the "You want to shoot off your foot ? Here have a howitzer!" of C++ nor the "well, we have a penknife. It's a bit rusty" of plain old 'C'. Any C program compiles without error under ObjC because ObjC is a formal superset of 'C', but you still get all the nice messaging/objects/categories/interfaces of a proper object-orientated language. With ObjC/Cocoa, it's hard *not* to write a decently-designed (probably M-V-C) application.

It may not have a "common runtime language", but you can (try to) prise ObjC/Cocoa out of my cold dead hands. Betcha can't.

Simon.

Those interested in GNUstep as a poor man's Yellow Box may be interested in a younger, more focused project: Cocotron. It seeks to clone Foundation and Appkit, and to provide tools to cross compile for other platforms with Xcode. It's a little Windows centric, but support for Linux, Solaris, and others seems to be in the works.