Update and jailbreak your iPhone OS 3.0. Tutorial here
Tap Cydia > Manage > Sources.
Tap Edit > Add.
and add the following sources. cydia.hackulo.us
it will prompt you for a source warning. just tap "Add Anyway"
wait until adding source is complete and tap "return to cydia"
you should see like this image:
Install AppSync for OS 3.0 by tapping the source that you just entered.
Cheers!!!!! you can now install your apps.