Source code for the XMP library can be obtained through git, see the page here:
http://sourceforge.net/projects/xmp/developAfter you clone the project to your local filesystem,
0) see the readme: \xmp\README
1) for examples to how they use the library, see the folder: \xmp\players\android\src\org\helllabs\android\xmp
2) see source code for the actual library: \xmp\src
Note: to find out the version of the library that comes with AndEngine, look at the file: \AndEngineMODPlayerExtension\jni\Makefile
Currently it is 3.3.0 (pre-release)