One comment added something I didn't think about before: "Does Apple really wish to preclude using lex/yacc in iPhone applications?"
Oh... but there are many more generators. Many apps that do networking may be partially built with some code generator for packet encoding/decoding.
I think people here have missed the quiet (but reasonable) explanation for the "no source languages but ours": that, to do background processing, Apple's going to have to assume that it completely controls and understands the runtime behavior of an app at the Obj-C runtime level.<p>Other runtimes (even those compiled to Obj-C, because they require additional runtime machinery) would break their assumptions, and thus their chance to do the low-level magic required to really throttle down apps.<p>Disappointing, yes. Was looking forward to MacRuby, but that won't happen until GC reaches the iPhone OS.
iPads will never replace PCs. They won't even replace all the other tablets on the market. There will be even more types of devices in the future to try new programming language techniques on than there are today. Be pissed about not being able to do what you want on iPhone OS, but it's pointless to imagine some future world where that's the only option.