จะโคลนเองทำได้นะ โหลด APK แล้วเปลี่ยน package name มาลงเอา
https://android.stackexchange.com/questions/19935/how-to-keep-two-versions-of-an-app-installed
It can be done, but not simple for the reasons eldarerathis mentioned. You need apktool. Refer to this guide on how to use it. And this on signing the apk after you're done.
You need to modify the AndroidManifest.xml file. Find the line that looks like this:
manifest package="com.example.app"
and change it to something like:
"com.example.app.foo"