Developers can directly obtain ASSIMP's source code via SVN. An anonymous checkout can be get using:
svn co https://assimp.svn.sourceforge.net/svnroot/assimp/trunk assimp
To view the source code in your browser, click here. Just remember: don't read source code :-)
Download
We provide both source code and precompiled binary packages for most platforms. Don't forget that you'll need boost to compile ASSIMP from scratch.
Download page