Does Apple allow the use of ad APIs other than its own?

Will apple allow an application that uses only 3rd party ad APIs like the following: https://github.com/mopub/mopub-client/wiki/IntegrationHowToIOS http://code.google.com/mobile/ads/docs/ios/fundamental开发者_StackOverflow中文版s.html to pass into its App Store?

Yes, they do, plenty of apps use non-iAd ads. You may also want to check out Millenial Media and Moblix.

Edit: And yes, as W Dyson says, you can maximize your revenue by using several networks at once, so that you'll always have an ad (iAds fill rate isn't 100%, so if you use them only, you'll end up not having an ad quite often).

If you look at some popular apps - like Words With Friends - you'll see that they sometimes show an iAd, but sometimes (probably even more often times) they show non-iAd ads, or even their own house ads about their other games.

If you're going to use iAd, you can check to see if you're being served a banner. If not, you can go to the other ad networks and request an ad. This gives you the most chances of having a banner served at all times. Always choose the ad networks in order of what makes you the most money.

Apple allows you to use other ad services. Some APIs, such as AdMob, will pull ads from multiple providers for you so you don't have to worry about finding a service that has an available ad.