This code is available free of charge from https://bitbucket.org/onyxmaster/mod_gridfs/.
Old driver that is written in C and used MongoDB C driver is still available in the "c-driver" branch.
+The latest pre-built binaries (mod_gridfs.so that you can place in your Apache modules directory) are available from https://bitbucket.org/onyxmaster/mod_gridfs/downloads.
Building (see next section for Ubuntu fast-forward instructions):
Make sure you have g++, SConstruct and boost libraries (filesystem, system, thread) installed