apktool will function. You do not even need to have to grasp the keystore to extract the source code (that's a bit Frightening). The key downside would be that the source is introduced in Smali format in lieu of Java. As per Fossdroid staff they get information from File-Droid http://downloadvideofromwhatsapp52213.is-blog.com/7415281/indicators-on-android-source-code-purchase-you-should-know