Some of the old 2.x SDK's "required" an Intel Mac... BUT were built by Apple as Universal binaries, and thus actually ran on newer PPC Macs running Leopard (after playing some tricks with the installer to ignore the "requirements").
Since the first SDK was released for 10.6 Snow Leopard, this is no longer true. And Apple no longer accepts apps built with the 2.x SDK, so a PPC is pretty much useless for current iOS development, except for a really old non-upgraded 2nd gen iPod Touch or something.