OpenBikeSharing APK's are hosted on GitHub in the Releases section.
They are signed with the developer's key and are the same as those distributed through Google Play.
osmdroid is a library used by OpenBikeSharing to display the maps. The tiles are downloaded and stored on your SD card the first time you browse the map to reduce bandwith later.
You can safely delete this directory, but the tiles will be downloaded again the next time you browse the map.