libdvdcss is a simple library designed for accessing DVDs like a block device
without having to bother about the decryption. The important features are: 

   - Portability. Currently supported platforms are GNU/Linux, FreeBSD, BeOS
     and Windows.
   - The MacOS X version is being worked on as well.
   - Simplicity. There are currently 7 functions in the API, and we intend to
     keep this number low.
   - Freedom. libdvdcss is released under the General Public License, ensuring
     it will stay free, and used only for free software products.
   - Just better. Unlike most similar projects, libdvdcss doesn't require the
     region of your drive to be set.

WWW: http://www.videolan.org/libdvdcss/