You will find the current version of Csound in http://sourceforge.net/projects/csound/files/csound6/. In the folder with the most recent version number you will find different files:
Building from source
Building Csound from source or from the git develop branch is not very difficult on Linux, and can also be done on Mac and Windows. How-to descriptions can be found in the BUILD.md file included with the Csound sources, also available online here.