The One Platform Foundation is a global open-source initiative whose aim is to help the Android ecosystem evolve by enabling developers to easily code and submit their apps across multiple alternative app stores. OPF’s first project is AppDF (App Description File), a format that allows developers to describe their Android application in one file and publish it to multiple app stores, dramatically cutting the time and effort required. The second project is OpenIAB (Open In-App Billing), a library that allows developers to support in-app billing APIs of multiple app stores with one piece of code.
Uploading an Android application to several app stores can be time-consuming. The AppDF format is designed to simplify this process. You describe your Android application once, create a simple AppDF archive that includes the XML description, APK file(s), screenshots, app icon, promo images, etc., and then just upload the file to all the stores that support AppDF.
There are several different In-App Purchase APIs already and their number is increasing. We are creating an open-source library that supports in-app purchase APIs of all the stores and provide an easy way for Android developers to develop their apps and games.
Its API is similar to Google Play
It is only 200kb and we're working on making it even smaller.
APK doesn't need to be recompiled to submit in another store.
Unity3d plugin with OpenIAB on board also supports iOS IAP.