iphone sdk for iphone os 2.1 final dmg does not install

Hi all,

opening the dmg file
iphone sdk for iphone os 2.1 final dmg
fails with the error -4960.
A small message box pops up defining this error.

Is it because I have a PowerPC still so that developing apps for the iPhone / iPod Touch is not possible, or is it due to a download problem? (I resumed the download a couple of times in Safari)

Thank you in advance for your help,
Thomas