When using multi-touch to scale, osmdroid behaves incorrectly. I also found the source code inside a jar file that uses a different license, and therefore I'm not sure I can use it.
There are Mapsforge. I believe the latest version has disabled online support, but you can still use it. I am not sure that you are resolving the situation for you.
http://code.google.com/p/mapsforge/
These 2 are the only free OpenStreetMaps AFAIK libraries.
You have already found osmdroid.
google api, (, ): https://developers.google.com/maps/documentation/android/
Android: http://bingmapsandroidsdk.codeplex.com/
mapforge ( openstreetmaps) http://code.google.com/p/mapsforge/
There will also be displayed. The biggest problem with all alternatives to the Google APIs is that all maps are unreadable on the HDPI + screen.
Nutiteq: https://github.com/nutiteq/hellomap3d
You can add your own map. Various sources of tiles.