ExtractAAR tries to read the minSdkVersion from the AndroidManifest.xml so it can create the project.properties file. You should have something like this:
<?xml version="1.0" encoding="utf-8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="com.everyplay.Everyplay">
<uses-sdk android:minSdkVersion="9"/>
</manifest>