The original iPhone, as it was presented in January 2007, was supposed

The original iPhone, as it was presented in January 2007, was supposed
to run only Web-Widget-Applications from third-party developers
(Dashboard widgets as introduced with Mac OS X 10.4). Only Apple's own
programs were supposed to have full access to the underlying operating
system that was derived from the then current Mac OS X 10.5 Leopard.

Under pressure from the developer community, Apple released in March
2008 a beta SDK for iPhone OS 1 which allowed programmers to create
native Cocoa applications for the iPhone ([link][1]). It was only
available for registered premium developers.

It was revealed for the first time the name of the operating system
running on the iPhone (iPhone OS) and its architecture. Apple had
ported its Mac OS X from PPC/Intel over to the ARM processor
architecture and had replaced the Application Kit framework layer,
which handled GUI application capabilities for mouse/keyboard
interaction, with the UIKit framework layer that allowed GUI
capabilities with touch/gesture user interaction, oriented to the
iPhone's touch screen. It allowed development of native iPhone
software on any Intel Macintosh with Xcode, either running on the
connected iPhone (compiling to ARM code, uploading to the iPhone and
remotely debugging) or running locally on the Mac running in the
iPhone simulator (compiling to Intel code and locally debugging). To
enable this, Apple provided all missing frameworks and runtime
libraries compiled for the Macintosh's architecture, so in reality,
the iPhone Simulator was running iPhone OS for Intel in contrast to
the iPhone OS for ARM on the iPhone.

As Apple released iPhone OS 2, in July 2008, the SDK was offered to
all who registered in a new iPhone developer program for $100 a year.
Membership included a license to install one's own programs to
registered iPhones for testing and to sell them at the new App Store.
Despite Apple's claim that the SDK was available for Intel Macs only,
some clever developers soon realized that all the frameworks and
programs the SDK delivered were compiled as Universal (PPC/Intel) code
while the compiler configuration files were ARM/Intel only. Moreover
the installer checked for Intel architecture and denied installation
on PPC Macs. Installing the .pkg archives manually and repairing the
compiler configurations made the iPhone SDK run completely on PPC
Macs. So the SDK was probably developed for both PPC and Intel Macs
and PPC support removed just before delivery because of marketing
reasons to boost the sales of the Intel Macs.

SDK 2.x was still compiled for Intel and PPC. Only with the release of
SDK 3.0 were the newer frameworks and applications compiled for Intel
alone, making it no longer possible to develop iPhone software on PPC
Macs. With the release of the original iPad in January 2010, Apple
chose to merge iPhone SDK with Xcode as a single download and removed
all prior separate iPhone SDKs that they had offered before from their
servers.

In spring 2014 the Wall Street Journal published an article named
"Inside a Secret Apple Room Where iPhone Software was Born" about the
development of the original iPhone's software, where it was shown in a
[picture][2] that it was developed on a blue-white Power Macintosh G3
because it had a similar low CPU power ([Link][3]).

This is a very rare software item of great historical interest, and
was the last version of the iPhone SDK installable and runnable fully
on a PPC Mac under Mac OS X Leopard.

* DL No 1: A disk image intended to trick the Xcode 3.1.1 release
with iPhone OS 2.2 to install the iPhone SDK packages on a PowerPC
host, also contains a diff to apply necessary modifications to an
xcspec file. [This can be done manually][4] without using this
package at all.
* DL No 2: Modified .dist file for tricking the installer, another
means of installing iPhone SDK packages on a PowerPC host. Not
necessary if you install the iPhone OS packages manually.
* DL No 3: Xcode 3.1.2 Release with (Intel Mac only) iPhone OS 2.2.1
SDK for Mac OS X version 10.5 (Leopard). Final release of the
iPhone SDK with PowerPC binaries.

Regardless of what means you use to install the iPhone SDK packages on
a PowerPC machine, you will still need to do some extra work to run
simulator binaries without an iPhone. One means is suggested in the
[Apple Xcode][5] entry's comments.

Articles on how to use iPhone 2.x SDK on PPC Macs:
[Screenshot iPhone simulator running on a G4 Mac][6]
[Step-by-Step guide for installation and compiling apps on a PPC Mac
with many screenshots (Spanish)][7]
[How to install iPhone SDK 2.2 on PPC with editing install script][4]
[How to install iPhone SDK 2.2 on PPC using Pacifist][8]
[Installation with little custom user script][9]
[Article with step-by-step instructions and many screenshots][10]
[According to this article the installation on PPC Macs works up to
SDK version 2.2.1, SDK 3.0 and higher not working since compiled for
Intel architecture only ][11]
[Installation procedure with full editing listings][12]
[installation procedure with screenshot of iPhone simulator and
provided file with above listing][13]

Compatibility
Architecture: PPC x86 (Intel:Mac)

Intel/G4/G5
Mac OS X 10.5.4 Leopard or higher
iPhone (2G) for remote debugging

[1]: http://www.engadget.com/2008/03/06/live-from-apples-iphone-press-conference/
[2]: http://s.wsj.net/public/resources/images/MK-CL082B_APPLE_G_20140325185022.jpg
[3]: http://blogs.wsj.com/digits/2014/03/25/inside-a-secret-apple-room-where-iphone-software-was-born/
[4]: http://www.chrishardie.com/2009/01/using-the-iphoneos-sdk-on-older-ppc-macs/
[5]: http://macintoshgarden.org/apps/apple-xcode
[6]: http://arstechnica.com/apple/2008/03/iphone-sdk-not-just-intel-only-anymore/
[7]: http://www.taringa.net/posts/mac/4426565/MAC-OS-X-instalar-el-iPhone-SDK-en-una-PowerPC-PowerBook-G4.html
[8]: http://reviews.cnet.com/8301-19512%5F7-10115416-233.html
[9]: http://alblue.bandlem.com/2008/12/enabling-iphone-development-on-ppc-macs.html
[10]: http://johnsofteng.wordpress.com/2009/09/05/howto-install-iphone-sdk-2-2-1-on-ppc-mac/
[11]: http://blog.barthe.ph/2009/03/01/iphone-sdk-ppc/
[12]: http://linuxclub.blogspot.de/2008/07/iphone-sdk-installtion-on-powerpc-g4.html
[13]: http://www.marco-maniscalco.de/?p=399