The source code is available on my github at misc-common/aesfs. To build just run 'python build.py' and the result is placed in ./build/aesfs/ and ./build/aespack/. AesPack is a command line utility to pack and unpack single files, while aesfs is a fuse file-system.
You can run aesfs with:
Since AesFS is on top your file-system you've to specify (with -o root) the directory where you want to store files, while the /mnt/ is the mount point where you can read/write your files in clear.
aesfs -o root=/my/plaindir /mnt/encrypted
Files are written in blocks of 4k (8 bytes of header, 16 extra bytes for aes, and 4072 bytes of data). Check block.h and block.c for more information.