I just uploaded "Show Firefox Passwords v1.12".
This will be my first app to test the waters of a dual licensing library.
It will work with Android Market Licensing AND AndroidPit App Center licensing.
I'm not totally sure about the first one working on Android <2.2 because
the Google code makes extensive use of android.utils.Base64 wich is only supported on API-level 8 and up.
I also extended the Android Market and AndroidPit AppCenter licensing-code to add translations to the very simple AndroidPit -code, cryptographic checks against tempering and set some traps so the code would detect if it has been tampered with the most common techniques.
Update: After a few weeks there where no complains. The app still sells fine. So everything seems to have worked well.
I also tried to hack a not-obfuscated version of it myself in Android Byte-code and compared to other apps (that I legitimately own) even though it's not obfuscated it's a pain in the *** to crack the licensing library itself.