The USB 2.0 specs are (pinout wise)...
Universal Serial Bus - Wikipedia, the free encyclopedia
USB pinout and wiring @ pinouts.ru
The 30 pin connector would appear to be like this
Apple iPod, iPad and iPhone dock - AllPinouts
So unless the USB end of the apple charging/data cable isn't USB 2.0 compliant (which surely it is) the only thing to ensure is that the non-apple charger is wired to USB 2.0 standard.