For example, some packages have licenses which prohibit commercial distribution. Others can be redistributed but are in fact shareware and not freeware. Users are welcome to use and test these packages, but are warned about their state of readiness. These include, for example, Perl scripts, or pure documentation. Currently this is done mainly for Atari and Amiga computers, and also for some VME based industry standard boards.
Source code is included for everything in the Debian system.
Moreover, the license terms of most programs in the system require that source code be distributed along with the programs, or that an offer to provide the source code accompany the programs. To retrieve the source code without having to be familiar with the structure of the FTP archive, try a command like apt-get source mypackagename . Historically, packages were kept in the subdirectory of dists corresponding to which distribution contained them. This turned out to cause various problems, such as large bandwidth consumption on mirrors when major changes were made. The dists directories are still used for the index files used by programs like apt .