Has anyone tried running the latest version of the iPhone SDK on 10.5.6 or below?

yeah man i can get it working on kalyway 10.5.2 system just do this
Look for the file

/System/Library/Coreservices/Systemversion.plist Copy it to your desktop, as a backup.

then edit the original one and find the following keys:

<key>ProductUserVisibleVersion</key>
<string>10.5.2</string>
<key>ProductVersion</key>
<string>10.5.2</string>

just replace the 10.5.2 with 10.5.7 and it should work.
http://www.brucebarrera.com/iphone-sdk-and-kalyway/ found from here

Thanks for the tip!

no prob did it work

Thank for your tip it did work on my hackintosh 10.5.6

the funny thing is I found this thread after crash my system because of updating :-)
so I reinstall my 10.5.6 again and try your trick it works!

I believe SDK3 requires at least 10.5.7. I'm trying to find a way to update my iPC 10.5.6 to 10.5.7. I would appreciate any help.